Fix random failure on TestReindex.shouldIndexDocument

org.elasticsearch.action.search.SearchPhaseExecutionException: Failed to execute phase [query_fetch], all shards failed
	at org.elasticsearch.action.search.type.TransportSearchTypeAction$BaseAsyncAction.onFirstPhaseResult(TransportSearchTypeAction.java:276)
	at org.elasticsearch.action.search.type.TransportSearchTypeAction$BaseAsyncAction$3.onFailure(TransportSearchTypeAction.java:222)
	at org.elasticsearch.search.action.SearchServiceTransportAction.sendExecuteFetch(SearchServiceTransportAction.java:307)
	at org.elasticsearch.action.search.type.TransportSearchQueryAndFetchAction$AsyncAction.sendExecuteFirstPhase(TransportSearchQueryAndFetchAction.java:71)
	at org.elasticsearch.action.search.type.TransportSearchTypeAction$BaseAsyncAction.performFirstPhase(TransportSearchTypeAction.java:214)
	at org.elasticsearch.action.search.type.TransportSearchTypeAction$BaseAsyncAction$2.run(TransportSearchTypeAction.java:188)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:745)

01:52:02,238 WARN  [ElasticSearchIndexingImpl] Skipping cmd because targetDocument is null {"id":"IndexingCommand-a73eb97c-9559-4b84-bf15-2e9ac50bad62","name":"ES_UPDATE","docId":null,"repo":null,"recurse":false,"sync":false}