Improve CCTEEqual()
Improve CCTEEqual()

We do not need to call FSubset() twice to check for equality.
Two CTE requirements will be considered equal if their lengths match and
one is subset of the other.

Signed-off-by: Dhanashree Kashid <c33208bbaddf93d98901a91e442046f89645c6bc@pivotal.io>

50wu/gpdb,PengJi/gporca-comments,greenplum-db/gporca,lisakowen/gpdb,greenplum-db/gporca,lisakowen/gpdb,adam8157/gpdb,xinzweb/gpdb,jmcatamney/gpdb,xinzweb/gpdb,greenplum-db/gpdb,adam8157/gpdb,jmcatamney/gpdb,lisakowen/gpdb,jmcatamney/gpdb,adam8157/gpdb,greenplum-db/gpdb,PengJi/gporca-comments,jmcatamney/gpdb,50wu/gpdb,50wu/gpdb,adam8157/gpdb,50wu/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,lisakowen/gpdb,50wu/gpdb,jmcatamney/gpdb,xinzweb/gpdb,greenplum-db/gpdb,xinzweb/gpdb,xinzweb/gpdb,greenplum-db/gpdb,xinzweb/gpdb,PengJi/gporca-comments,jmcatamney/gpdb,jmcatamney/gpdb,50wu/gpdb,PengJi/gporca-comments,lisakowen/gpdb,greenplum-db/gporca,greenplum-db/gpdb,50wu/gpdb,greenplum-db/gpdb,adam8157/gpdb,greenplum-db/gporca,lisakowen/gpdb,adam8157/gpdb,PengJi/gporca-comments,lisakowen/gpdb,xinzweb/gpdb,xinzweb/gpdb,lisakowen/gpdb,adam8157/gpdb,adam8157/gpdb,50wu/gpdb,greenplum-db/gpdb