title: WARNING - State of this instance has been externally set to success. Taking the poison pill
body: <p>I have recently upgraded my Airflow cluster from 1.7.1.3 to 1.10.2 with mysql as backend and rabbitmq for message passing. After upgrading i am seeing this issue in some of my tasks -</p>
  
  <pre><code>WARNING - State of this instance has been externally set to success. Taking the poison pill.
  </code></pre>
  
  <p>This randomly comes once in a while in any task. I have not marked this task success externally but still i am getting this error. Has anyone else faced this? How to fix this ?</p>