Fix gpload reuse table issues (#1693)
Fix gpload reuse table issues (#1693)

* Fix gpload reuse table issues

This commit fixes issues below:

1, reports unexpected error when reuse_table is enabled
2, doesn't recognize GPDB delimiter syntax like E'\t'
3, unnecessary case sensible of column names

Signed-off-by: Adam Lee <b42a6d93d796915222f6ffb2ffdd6137d93c1cdb@pivotal.io>
Signed-off-by: Ning Wu <57195575ccb690f85902294025b39c9888c369e6@pivotal.io>

* delimiter '\t' handled

* Fixed report warnings wrongly when reusable table exists

* remove the tailing space and simplify sql

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