title: Elasticsearch snapshot IN_PROGRESS for long time, delete snapshot is also not working
body: <p>I'm using Elasticsearch 5.1.1 and we have a daily snapshot process running. The last snapshot have been created few days ago and its status is still <em>IN_PROGRESS</em>.</p>
  
  <p>I tried to delete via snapshot api but it fails. Also I'm unable to take new snapshot due to snapshot in progress exception. Please help me to resolve this issue.</p>
  
  <p>Thanks in advance.</p>