HBASE-9498 NPE in HBaseAdmin if master not running

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1521902 13f79535-47bb-0310-9956-ffa450edef68
HBASE-9468 Previous active master can still serves RPC request when it is trying recovering expired zk session

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1521949 13f79535-47bb-0310-9956-ffa450edef68
HBASE-9468 Previous active master can still serves RPC request when it is trying recovering expired zk session

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1521959 13f79535-47bb-0310-9956-ffa450edef68
HBASE-9462 HBaseAdmin#isTableEnabled() should throw exception for non-existent table



git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1522010 13f79535-47bb-0310-9956-ffa450edef68