Fix attribute numbers in the response to BASE_BACKUP command.
Fix attribute numbers in the response to BASE_BACKUP command.

In GPDB, there used to be an extra column in the result set. That was
removed as part of the walreplication work, so it now matches the
upstream. But forgot to update these PQgetvalue() calls in pg_basebackup
accordingly.

Based on @macroyuyang's original patch and diagnosis.

ashwinstar/gpdb,Chibin/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,lisakowen/gpdb,jmcatamney/gpdb,xinzweb/gpdb,lisakowen/gpdb,Chibin/gpdb,50wu/gpdb,adam8157/gpdb,ashwinstar/gpdb,lisakowen/gpdb,ashwinstar/gpdb,xinzweb/gpdb,lisakowen/gpdb,lisakowen/gpdb,adam8157/gpdb,Chibin/gpdb,50wu/gpdb,adam8157/gpdb,50wu/gpdb,50wu/gpdb,adam8157/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,50wu/gpdb,xinzweb/gpdb,Chibin/gpdb,adam8157/gpdb,xinzweb/gpdb,jmcatamney/gpdb,Chibin/gpdb,50wu/gpdb,adam8157/gpdb,ashwinstar/gpdb,xinzweb/gpdb,Chibin/gpdb,greenplum-db/gpdb,50wu/gpdb,Chibin/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,lisakowen/gpdb,Chibin/gpdb,Chibin/gpdb,xinzweb/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,adam8157/gpdb,Chibin/gpdb,xinzweb/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,adam8157/gpdb,ashwinstar/gpdb,xinzweb/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,50wu/gpdb,lisakowen/gpdb,lisakowen/gpdb,jmcatamney/gpdb