Fix setting latestCompletedXid on subtransaction abort.
Fix setting latestCompletedXid on subtransaction abort.

QE readers are not required to participate in any transaction activity like
commit or abort. There counter part QE writer is responsible for performing the
same. This commit is just fixing the over-sight caused by commit a453004, as
anyways for QE reader case we will return much earlier in function and never
ever reach here.

Fixes issue #1275 reported by @pengzhout.

ashwinstar/gpdb,Chibin/gpdb,cjcjameson/gpdb,edespino/gpdb,Quikling/gpdb,greenplum-db/gpdb,lisakowen/gpdb,edespino/gpdb,cjcjameson/gpdb,rvs/gpdb,jmcatamney/gpdb,kaknikhil/gpdb,cjcjameson/gpdb,lintzc/gpdb,kaknikhil/gpdb,greenplum-db/gpdb,janebeckman/gpdb,janebeckman/gpdb,xinzweb/gpdb,lintzc/gpdb,kaknikhil/gpdb,rvs/gpdb,yuanzhao/gpdb,50wu/gpdb,Quikling/gpdb,janebeckman/gpdb,xinzweb/gpdb,jmcatamney/gpdb,adam8157/gpdb,Chibin/gpdb,yuanzhao/gpdb,Chibin/gpdb,greenplum-db/gpdb,kaknikhil/gpdb,edespino/gpdb,lisakowen/gpdb,yuanzhao/gpdb,Quikling/gpdb,xinzweb/gpdb,janebeckman/gpdb,ashwinstar/gpdb,adam8157/gpdb,cjcjameson/gpdb,edespino/gpdb,greenplum-db/gpdb,lintzc/gpdb,xinzweb/gpdb,kaknikhil/gpdb,greenplum-db/gpdb,50wu/gpdb,rvs/gpdb,ashwinstar/gpdb,Chibin/gpdb,kaknikhil/gpdb,adam8157/gpdb,Chibin/gpdb,Chibin/gpdb,50wu/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,yuanzhao/gpdb,jmcatamney/gpdb,kaknikhil/gpdb,edespino/gpdb,lisakowen/gpdb,greenplum-db/gpdb,janebeckman/gpdb,jmcatamney/gpdb,adam8157/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,kaknikhil/gpdb,lintzc/gpdb,Quikling/gpdb,edespino/gpdb,adam8157/gpdb,edespino/gpdb,edespino/gpdb,kaknikhil/gpdb,jmcatamney/gpdb,lisakowen/gpdb,xinzweb/gpdb,edespino/gpdb,janebeckman/gpdb,rvs/gpdb,rvs/gpdb,ashwinstar/gpdb,rvs/gpdb,cjcjameson/gpdb,Chibin/gpdb,ashwinstar/gpdb,lisakowen/gpdb,50wu/gpdb,yuanzhao/gpdb,50wu/gpdb,greenplum-db/gpdb,xinzweb/gpdb,adam8157/gpdb,Quikling/gpdb,lisakowen/gpdb,cjcjameson/gpdb,lintzc/gpdb,xinzweb/gpdb,yuanzhao/gpdb,lintzc/gpdb,Quikling/gpdb,50wu/gpdb,janebeckman/gpdb,50wu/gpdb,lintzc/gpdb,50wu/gpdb,Quikling/gpdb,adam8157/gpdb,rvs/gpdb,lisakowen/gpdb,Chibin/gpdb,edespino/gpdb,Quikling/gpdb,janebeckman/gpdb,jmcatamney/gpdb,yuanzhao/gpdb,Quikling/gpdb,xinzweb/gpdb,rvs/gpdb,Chibin/gpdb,lintzc/gpdb,cjcjameson/gpdb,yuanzhao/gpdb,kaknikhil/gpdb,janebeckman/gpdb,Quikling/gpdb,jmcatamney/gpdb,cjcjameson/gpdb,janebeckman/gpdb,Chibin/gpdb,lisakowen/gpdb,adam8157/gpdb,cjcjameson/gpdb,greenplum-db/gpdb,yuanzhao/gpdb,yuanzhao/gpdb,cjcjameson/gpdb,lintzc/gpdb,rvs/gpdb,rvs/gpdb