title: Timeout on deleting a snapshot repository
body: <p>I'm running elasticsearch 1.7.5 w/ 19 nodes (12 data nodes). </p>
  
  <p>Attempting to setup snapshots for backup and recovery - but am getting a 503 on creation and deletion of a snapshot repository. </p>
  
  <pre><code>curl -XDELETE 'localhost:9200/_snapshot/backups?pretty'
  </code></pre>
  
  <p>returns: </p>
  
  <pre><code>{
   "error" : "RemoteTransportException[[masternodename][inet[/10.0.0.20:9300]][cluster:admin/repository/delete]]; nested: ProcessClusterEventTimeoutException[failed to process cluster event (delete_repository [backups]) within 30s]; ",
   "status" : 503
  }
  </code></pre>
  
  <p>I was able to adjust the query w/ a master_timeout=10m - still getting a timeout. Is there a  way to debug the cause of this request failing? </p>