HBASE-9926 Scanner doesn't check if a region is available

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1540883 13f79535-47bb-0310-9956-ffa450edef68
HBASE-9952 Snapshot restore may fail due to NullPointerException

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1540909 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-HBASE-8584-trunk-gd