Don't turn attr="all" into a list

pkg_resource.format_pkg_list expects its `attr` argument to be either a
list of attributes or the string "all" to indicate all available
attributes should be used for formatting.

Fixes: saltstack#62032

changelog/62032.fixed

@@ -0,0 +1 @@
+Fix attr=all handling in pkg.list_pkgs() (yum/zypper).

salt/modules/yumpkg.py

@@ -735,7 +735,7 @@ def list_pkgs(versions_as_list=False, **kwargs):
         return {}
 
     attr = kwargs.get("attr")
-    if attr is not None:
+    if attr is not None and attr != "all":
         attr = salt.utils.args.split_input(attr)
 
     contextkey = "pkg.list_pkgs"

salt/modules/zypperpkg.py

@@ -914,7 +914,7 @@ def list_pkgs(versions_as_list=False, root=None, includes=None, **kwargs):
         return {}
 
     attr = kwargs.get("attr")
-    if attr is not None:
+    if attr is not None and attr != "all":
         attr = salt.utils.args.split_input(attr)
 
     includes = includes if includes else []