title: version_conflict_engine_exception with multiple _update_by_query
body: <p>I have situation where i am getting <code>version_conflict_engine_exception</code>. I have daemon which continuously pushing data for update to elasticsearch. I am using <code>_updat_by_query</code>. Here is the sample call:</p>
  
  <pre><code>curl -XPOST 'localhost:9200/my_index/my_type/_update_by_query?pretty' -H 'Content-Type: application/json' -d '
  {
     "query":{
        "term":{
           "userid":1234
        }
     },
     "script":{
        "lang":"painless",
        "inline":"if (ctx._source.containsKey(\"newfield\")) {ctx._source.newfiled.add(params.value)} else {ctx._source.newfield = [params.value]}",
        "params":{
           "value":{"new":"value"}
        }
     }
  }'
  </code></pre>
  
  <p>Whenever i have same userid (on <code>query.terms</code>), there is multiple update query hits one after another and it gives me error <code>version_conflict_engine_exception</code> . I know its because of version conflicting but how we can overcome from this where i have frequently update queries. I also not finding any <code>bulk</code> option for <code>_update_by_query</code>. I am getting following error:</p>
  
  <pre><code>{
      "took": 1,
      "timed_out": false,
      "total": 1,
      "updated": 0,
      "deleted": 0,
      "batches": 1,
      "version_conflicts": 1,
      "noops": 0,
      "retries": {
          "bulk": 0,
          "search": 0
      },
      "throttled_millis": 0,
      "requests_per_second": -1.0,
      "throttled_until_millis": 0,
      "failures": [{
          "index": "my_index",
          "type": "my_type",
          "id": "Gc-_SWIBUzg1_4kxJ5uD",
          "cause": {
              "type": "version_conflict_engine_exception",
              "reason": "[logs][Gc-_SWIBUzg1_4kxJ5uD]: version conflict, current version [2] is different than the one provided [1]",
              "index_uuid": "dbtt5uS9R3ClcPt6Oar1MQ",
              "shard": "3",
              "index": "my_index"
          },
          "status": 409
      }]
  }
  </code></pre>