HBASE-9697 ZKDataMigrator should exit on table(s) null check.

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1528329 13f79535-47bb-0310-9956-ffa450edef68
HBASE-9676 AsyncProcess can create more tasks than hbase.client.max.total.tasks

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1528340 13f79535-47bb-0310-9956-ffa450edef68