fix: memory leak (#60)

Author: luislhl

txstratum/protocol.py

@@ -186,6 +186,8 @@ def connection_lost(self, exc: Optional[Exception]) -> None:
             asyncio.ensure_future(self.estimator_task.stop())
         if self.refresh_job_task:
             asyncio.ensure_future(self.refresh_job_task.stop())
+        if self.messages_timeout_task:
+            asyncio.ensure_future(self.messages_timeout_task.stop())
 
     def ask_miner_to_reconnect(self) -> None:
         """Ask the miner to reconnect. We just want to force it to disconnect with this."""