Don't use all task params for vars, just the module args

lib/ansible/playbook/task.py

@@ -197,7 +197,8 @@ class Task(Base, Conditional, Taggable, Become):
         if self._task_include:
             all_vars.update(self._task_include.get_vars())
 
-        all_vars.update(self.serialize())
+        if isinstance(self.args, dict):
+            all_vars.update(self.args)
 
         if 'tags' in all_vars:
             del all_vars['tags']