SOLR-4570: Even if an explicit shard id is used, ZkController#preRegister should still wait to see the shard id in it's current ClusterState.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_2@1458114 13f79535-47bb-0310-9956-ffa450edef68