HIVE-8166 : CBO: 1) Bailout in strict mode 2) OB,LIMIT RR table alias is same as that of sub query 3) If RowCount Not found then fall back to non cbo 4)Fix NPE in unique col name check (John Pullokkaran via Ashutosh Chauhan)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/cbo@1625852 13f79535-47bb-0310-9956-ffa450edef68