Fix the issue when initializing SPIMemReserved.
Fix the issue when initializing SPIMemReserved.

When resource group is enabled, initialization of
SPIMemReserved should not depend on statement_mem.
Chibin/gpdb,jmcatamney/gpdb,yuanzhao/gpdb,adam8157/gpdb,jmcatamney/gpdb,yuanzhao/gpdb,ashwinstar/gpdb,50wu/gpdb,yuanzhao/gpdb,Chibin/gpdb,edespino/gpdb,edespino/gpdb,xinzweb/gpdb,xinzweb/gpdb,edespino/gpdb,greenplum-db/gpdb,50wu/gpdb,edespino/gpdb,adam8157/gpdb,50wu/gpdb,ashwinstar/gpdb,xinzweb/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,Chibin/gpdb,adam8157/gpdb,lisakowen/gpdb,yuanzhao/gpdb,Chibin/gpdb,adam8157/gpdb,edespino/gpdb,xinzweb/gpdb,edespino/gpdb,jmcatamney/gpdb,Chibin/gpdb,ashwinstar/gpdb,edespino/gpdb,lisakowen/gpdb,greenplum-db/gpdb,lisakowen/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,lisakowen/gpdb,edespino/gpdb,yuanzhao/gpdb,Chibin/gpdb,greenplum-db/gpdb,adam8157/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,yuanzhao/gpdb,xinzweb/gpdb,lisakowen/gpdb,greenplum-db/gpdb,Chibin/gpdb,yuanzhao/gpdb,edespino/gpdb,adam8157/gpdb,50wu/gpdb,jmcatamney/gpdb,50wu/gpdb,xinzweb/gpdb,Chibin/gpdb,jmcatamney/gpdb,Chibin/gpdb,ashwinstar/gpdb,50wu/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,Chibin/gpdb,adam8157/gpdb,lisakowen/gpdb,edespino/gpdb,yuanzhao/gpdb,xinzweb/gpdb,50wu/gpdb,adam8157/gpdb,50wu/gpdb,yuanzhao/gpdb,yuanzhao/gpdb,lisakowen/gpdb,lisakowen/gpdb,xinzweb/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,greenplum-db/gpdb