Two fixes to action plugins

* Fix the task_vars parameter to not default to a mutable type (dict)
* Implement invocation in the base class's run() method have each action
  module call the run() method's implemention in the base class.
* Return values from the action plugins' run() method takes the return
  value from the base class run() method into account so that invocation
  makes its way to the output.

Fixes #12869

lib/ansible/plugins/action/fail.py

@@ -20,16 +20,22 @@ __metaclass__ = type
 
 from ansible.plugins.action import ActionBase
 
+
 class ActionModule(ActionBase):
     ''' Fail with custom message '''
 
     TRANSFERS_FILES = False
 
-    def run(self, tmp=None, task_vars=dict()):
+    def run(self, tmp=None, task_vars=None):
+        if task_vars is None:
+            task_vars = dict()
+
+        result = super(ActionModule, self).run(tmp, task_vars)
 
         msg = 'Failed as requested from task'
         if self._task.args and 'msg' in self._task.args:
             msg = self._task.args.get('msg')
 
-        return dict(failed=True, msg=msg)
-
+        result['failed'] = True
+        result['msg'] = msg
+        return result