SOLR-3511 make sure parent node exits before using the queue, check leader status before every update when in fallback mode
SOLR-3511 make sure parent node exits before using the queue, check leader status before every update when in fallback mode

git-svn-id: 308d55f399f3bd9aa0560a10e81a003040006c48@1348760 13f79535-47bb-0310-9956-ffa450edef68

cscorley/solr-only-mirror,cscorley/solr-only-mirror,cscorley/solr-only-mirror