The problem query here has a HAVING clause which is const and resolves
to a TRUE value. The HAVING condition is thus eliminated and replaced
with a NULL pointer. However, the query then looses state as an
"aggregated" query, and deletion is attempted, even though
aggregation is not allowed in a DELETE statement.

The solution is to leave a TRUE condition in HAVING so that query block
is still aggregated.

Also move const elimination of HAVING to after ROLLUP resolving,
since it may affect the nullability of the HAVING condition.

Reviewed by: Chaithra Gopalareddy <chaithra.gopalareddy@oracle.com>