HBASE-12634 Fix the AccessController#requireGlobalPermission(ns) with NS

Signed-off-by: Matteo Bertozzi <matteo.bertozzi@cloudera.com>
HBASE-12635 Delete acl notify znode of table after the table is deleted (Liu Shaohui)
HBASE-12619 Backport HBASE-11639 (Replicate the visibility of Cells as strings) to 0.98 (Ramkrishna S. Vasudevan)
Merge remote-tracking branch 'remotes/origin/0.98' into 0.98