refactor gpcheckcat foreign key validation (#1230)
refactor gpcheckcat foreign key validation (#1230)

* refactor gpcheckcat foreign key validation to improve readability

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