Fix AC-969, Convert variables element in changes dictionary from json representation

awx/api/serializers.py

@@ -1037,6 +1037,8 @@ class ActivityStreamSerializer(BaseSerializer):
             return {}
         try:
             d_changes = json.loads(obj.changes)
+            if 'variables' in d_changes:
+                d_changes['variables'] = json.loads(d_changes['variables'])
             return d_changes
         except Exception, e:
             logger.warn("Error deserializing activity stream json changes")