SOLR-6426: SolrZkClient clean can fail due to a race with children nodes.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1620246 13f79535-47bb-0310-9956-ffa450edef68
SOLR-5596: Raise zk client timeout for mock objects.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1620248 13f79535-47bb-0310-9956-ffa450edef68