HBASE-8355: BaseRegionObserver#pre(Compact|Flush|Store)ScannerOpen returns null (Andrew Purtell, Jesse Yates)

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.95@1483095 13f79535-47bb-0310-9956-ffa450edef68
HBASE-8435 Test for zk leak does not account for unsynchronized access to zk watcher: ADDENDUM

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.95@1483118 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/0.95' into 0.95-gd
Merge remote branch 'origin/0.95-gd' into fb-YAHOO-317-0.95-gd