HBASE-8590 [0.94] BlockingMetaScannerVisitor should check for parent meta entry while waiting for split daughter

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.94@1489691 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/0.94' into 0.94-gd