IMPALA-1065: Running explain on attached (TPC-DS) query throws
IllegalStateExcpetion

This commit resolves IMPALA-1065 where the explain statement of TPC-DS
Q48 resulted in an IllegalStateException due to an overflow in the
cardinality estimation of a cross join operator. The fix is to check if
an overflow has occurred and reset the cardinality estimation to a valid
value.

Change-Id: I0e88fde07e7a5d86819af317e98bab7ac08d5a8a
Reviewed-on: http://gerrit.ent.cloudera.com:8080/3346
Reviewed-by: Dimitris Tsirogiannis <dtsirogiannis@cloudera.com>
Tested-by: jenkins