HBASE-9510 Namespace operations should throw clean exceptions

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1523902 13f79535-47bb-0310-9956-ffa450edef68
HBASE-9510 Namespace operations should throw clean exceptions

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1523903 13f79535-47bb-0310-9956-ffa450edef68