SOLR-5608: Don't allow a closed SolrCore to publish state to ZooKeeper.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1555659 13f79535-47bb-0310-9956-ffa450edef68
SOLR-5608: Unregister core from cloud state after closing in unload.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1555685 13f79535-47bb-0310-9956-ffa450edef68
fix test bug; remove dead code

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1555715 13f79535-47bb-0310-9956-ffa450edef68
remove redundant cast

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1555719 13f79535-47bb-0310-9956-ffa450edef68