Fix defaults for immutability of MiddlewareServers

This commit backports the change extracted to
manageiq-providers-hawkular, for use with the 5.8 release of CloudForms.
It is meant to be replaced later with a type column in the affected
models, allowing the proper use of STI.

app/models/middleware_server.rb

@@ -42,11 +42,11 @@ def in_domain?
 
   # Returns whether a server is immutable or not.
   #
-  # By default, we define all servers as being immutable, so that power
-  # operations are not allowed, and it is the provider responsability to
+  # By default, we define all servers as being mutable, so that power
+  # operations are allowed, and it is the provider responsability to
   # reimplement this method if necessary.
   def immutable?
-    true
+    properties['Immutable'] == 'true'
   end
 
   # Returns whether a server is immutable or not.

spec/models/middleware_server_spec.rb

@@ -27,8 +27,18 @@
   end
 
   describe '#immutable?' do
-    it 'is always true' do
-      expect(server).to be_immutable
+    it 'is true if "Immutable" is set as true' do
+      subject.properties = { 'Immutable' => 'true' }
+      expect(subject).to be_immutable
+    end
+
+    it 'is false if "Immutable" is set as false' do
+      subject.properties = { 'Immutable' => 'false' }
+      expect(subject).not_to be_immutable
+    end
+
+    it 'is false if no keys are defined' do
+      expect(subject).not_to be_immutable
     end
   end