HBASE-8547. Fix java.lang.RuntimeException: Cached an already cached block (Addendum2 and 3)

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.94@1484034 13f79535-47bb-0310-9956-ffa450edef68
HBASE-8539 ADDENDUM Double(or tripple ...) ZooKeeper listeners of the same type when Master recovers from ZK SessionExpiredException (Jeffrey Zhong)

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.94@1484041 13f79535-47bb-0310-9956-ffa450edef68