gpexpand: refactor table_expand_error global variable
gpexpand: refactor table_expand_error global variable

Remove global variable table_expand_error by checking the pool of done
ExpandCommand(s).

Signed-off-by: Marbin Tan <fe9db60e23a06449b90b19d66b721708068089ad@pivotal.io>

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