Fixed tests when run with zope.component 5+.

Same test failure:

```
File "/Users/maurits/community/plone-coredev/6.0/src/plone.app.users/plone/app/users/tests/password.rst", line 27, in password.rst
Failed example:
    browser.open('http://nohost/plone/' + view_name)
Expected:
    Traceback (most recent call last):
    ...
    zExceptions.unauthorized.Unauthorized: ...You are not authorized to access this resource...
Got:
    Traceback (most recent call last):
      File "/Users/maurits/.pyenv/versions/3.9.9/lib/python3.9/doctest.py", line 1334, in __run
        exec(compile(example.source, filename, "single",
      File "<doctest password.rst[8]>", line 1, in <module>
        browser.open('http://nohost/plone/' + view_name)
      File "/Users/maurits/shared-eggs/cp39/zope.testbrowser-5.5.1-py3.9.egg/zope/testbrowser/browser.py", line 256, in open
        self._processRequest(url, make_request)
      File "/Users/maurits/shared-eggs/cp39/zope.testbrowser-5.5.1-py3.9.egg/zope/testbrowser/browser.py", line 282, in _processRequest
        resp = make_request(reqargs)
      File "/Users/maurits/shared-eggs/cp39/zope.testbrowser-5.5.1-py3.9.egg/zope/testbrowser/browser.py", line 253, in make_request
        return self.testapp.get(url, **args)
      File "/Users/maurits/shared-eggs/cp39/WebTest-3.0.0-py3.9.egg/webtest/app.py", line 324, in get
        return self.do_request(req, status=status,
      File "/Users/maurits/shared-eggs/cp39/zope.testbrowser-5.5.1-py3.9.egg/zope/testbrowser/browser.py", line 93, in do_request
        response = super(TestbrowserApp, self).do_request(req, status,
      File "/Users/maurits/shared-eggs/cp39/WebTest-3.0.0-py3.9.egg/webtest/app.py", line 620, in do_request
        res = req.get_response(app, catch_exc_info=True)
      File "/Users/maurits/shared-eggs/cp39/WebOb-1.8.7-py3.9.egg/webob/request.py", line 1309, in send
        status, headers, app_iter, exc_info = self.call_application(
      File "/Users/maurits/shared-eggs/cp39/WebOb-1.8.7-py3.9.egg/webob/request.py", line 1278, in call_application
        app_iter = application(self.environ, start_response)
      File "/Users/maurits/shared-eggs/cp39/WebTest-3.0.0-py3.9.egg/webtest/lint.py", line 196, in lint_app
        iterator = application(environ, start_response_wrapper)
      File "/Users/maurits/shared-eggs/cp39/plone.testing-8.0.3-py3.9.egg/plone/testing/_z2_testbrowser.py", line 39, in wrapped_func
        return func(*args, **kw)
      File "/Users/maurits/shared-eggs/cp39/plone.testing-8.0.3-py3.9.egg/plone/testing/_z2_testbrowser.py", line 66, in __call__
        wsgi_result = publish(environ, start_response)
      File "/Users/maurits/community/plone-coredev/6.0/src/Zope/src/ZPublisher/WSGIPublisher.py", line 391, in publish_module
        request.close()
      File "/Users/maurits/community/plone-coredev/6.0/src/Zope/src/ZPublisher/BaseRequest.py", line 215, in close
        notify(EndRequestEvent(None, self))
      File "/Users/maurits/shared-eggs/cp39/zope.event-4.5.0-py3.9.egg/zope/event/__init__.py", line 32, in notify
        subscriber(event)
      File "/Users/maurits/shared-eggs/cp39/zope.component-5.0.1-py3.9.egg/zope/component/event.py", line 27, in dispatch
        component_subscribers(event, None)
      File "/Users/maurits/shared-eggs/cp39/zope.component-5.0.1-py3.9.egg/zope/component/_api.py", line 134, in subscribers
        return sitemanager.subscribers(objects, interface)
      File "/Users/maurits/shared-eggs/cp39/zope.interface-5.4.0-py3.9-macosx-10.15-x86_64.egg/zope/interface/registry.py", line 448, in subscribers
        return self.adapters.subscribers(objects, provided)
      File "/Users/maurits/shared-eggs/cp39/zope.interface-5.4.0-py3.9-macosx-10.15-x86_64.egg/zope/interface/adapter.py", line 895, in subscribers
        subscriptions = self.subscriptions([providedBy(o) for o in objects], provided)
      File "/Users/maurits/shared-eggs/cp39/zope.interface-5.4.0-py3.9-macosx-10.15-x86_64.egg/zope/interface/adapter.py", line 877, in _uncached_subscriptions
        if order >= len(byorder):
      File "/Users/maurits/.pyenv/versions/3.9.9/lib/python3.9/collections/__init__.py", line 1169, in __len__
        return len(self.data)
      File "/Users/maurits/shared-eggs/cp39/ZODB-5.6.0-py3.9.egg/ZODB/Connection.py", line 785, in setstate
        raise ConnectionStateError(msg)
    ZODB.POSException.ConnectionStateError: Shouldn't load state for persistent.list.PersistentList 0x3953f62e87808eb2 when the connection is closed
```

Should be somehow caused by this zope.component PR:
zopefoundation/zope.component#51

From what I can follow from the traceback and running around in the pdb, it goes wrong in this part of `ZPublisher/BaseRequest.py`:

```
    def close(self):
        try:
            notify(EndRequestEvent(None, self))
        finally:
            # subscribers might need the zodb, so `clear` must come afterwards
            # (since `self._held=None` might close the connection, see above)
            self.clear()
```

The notify fails, even when I comment out the two subscribers that I found (`Products.Five` and `plone.app.contentrules`).
Probably some other code has already called `self.clear()` before this.
A reason for this can be that several subrequests are made for the Diazo theme, and this seems to call `self.clear()` directly.
Whatever the reason, the comment is true: subscribers might need the zodb.
In fact, with zope.component 5, the list of subscribers itself, even when it is empty, is something that we get from the zodb.
So it fails here.

When I run `bin/instance fg` and visit the same page anonymously (`@@change-password`) it works fine:
I am Unauthorized and get redirected, which is also what the test expects.
So in practice all seems fine.

So what somehow triggers the ZODB error, is that this is a test, and the first browser visit is to a page that raises an Unauthorized.
The fix/workaround is to first visit the root of the site.  Then somehow all is well.

Note: last time I tried this, most tests in most packages passed just fine.
`plone.app.users` was an exception, and there were about two other packages I think.
I will follow up with more PRs, but this one should be fine, also for use with our current outdated zope.component 4.6.2.

news/500.bugfix

@@ -0,0 +1,2 @@
+Fixed tests when run with ``zope.component`` 5+.
+[maurits]

plone/app/users/tests/password.rst

@@ -19,6 +19,12 @@ Set up
     >>> browser = Browser(app)
     >>> browser.handleErrors = False
 
+We must first view the homepage, otherwise we get a weird error with zope.component 5+:
+ZODB.POSException.ConnectionStateError: Shouldn't load state for persistent.list.PersistentList 0x... when the connection is closed
+
+    >>> browser.open('http://nohost/plone/')
+
+
 The view
 ========
 

plone/app/users/tests/personal_preferences.rst

@@ -24,6 +24,11 @@ Set up
     ...     if len(v) != 1: return False
     ...     return v[0] == empty_marker
 
+We must first view the homepage, otherwise we get a weird error with zope.component 5+:
+ZODB.POSException.ConnectionStateError: Shouldn't load state for persistent.list.PersistentList 0x... when the connection is closed
+
+    >>> browser.open('http://nohost/plone/')
+
 Viewing the personal preferences
 --------------------------------
 

plone/app/users/tests/userdata.rst

@@ -19,6 +19,12 @@ Set Up
     >>> browser = Browser(app)
     >>> browser.handleErrors = False
 
+We must first view the homepage, otherwise we get a weird error with zope.component 5+:
+ZODB.POSException.ConnectionStateError: Shouldn't load state for persistent.list.PersistentList 0x... when the connection is closed
+
+    >>> browser.open('http://nohost/plone/')
+
+
 Viewing the  personal information
 ---------------------------------