SOLR-4705: Fixed bug causing NPE when querying a single replica in SolrCloud using the shards param (merge r1476310 and r1476328 via '-r 1476309:1476328' from trunk)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_3@1476340 13f79535-47bb-0310-9956-ffa450edef68