Refactor 'mirror' message enveloping to use new serialization

lib/tfw/networking/event_handlers/server_connector.py

@@ -30,8 +30,9 @@ class ServerUplinkConnector(ZMQConnectorBase):
         self._zmq_push_socket.connect('tcp://localhost:{}'.format(TFWENV.RECEIVER_PORT))
 
     def send_to_eventhandler(self, message):
-        message['data']['key'] = message['key']
+        nested_message = {'key': message['key'], 'data': message.pop('data')}
         message['key'] = 'mirror'
+        message['data'] = nested_message
         self.send(message)
 
     def send(self, message):