Move gp_optimizer test to a different parallel group.
Move gp_optimizer test to a different parallel group.

This is to fix intermittent failures due to 'too many clients'
error when the test is run with a large parallel group.

Closes #222.

xinzweb/gpdb,yuanzhao/gpdb,janebeckman/gpdb,Chibin/gpdb,randomtask1155/gpdb,royc1/gpdb,Quikling/gpdb,chrishajas/gpdb,lpetrov-pivotal/gpdb,rvs/gpdb,rubikloud/gpdb,lisakowen/gpdb,tangp3/gpdb,edespino/gpdb,zaksoup/gpdb,lintzc/gpdb,tangp3/gpdb,foyzur/gpdb,tangp3/gpdb,rubikloud/gpdb,CraigHarris/gpdb,cjcjameson/gpdb,adam8157/gpdb,zaksoup/gpdb,rvs/gpdb,Quikling/gpdb,kaknikhil/gpdb,xuegang/gpdb,Quikling/gpdb,yuanzhao/gpdb,tangp3/gpdb,royc1/gpdb,adam8157/gpdb,zaksoup/gpdb,zaksoup/gpdb,janebeckman/gpdb,jmcatamney/gpdb,CraigHarris/gpdb,rubikloud/gpdb,CraigHarris/gpdb,50wu/gpdb,0x0FFF/gpdb,ashwinstar/gpdb,kaknikhil/gpdb,rubikloud/gpdb,Chibin/gpdb,0x0FFF/gpdb,Quikling/gpdb,tangp3/gpdb,chrishajas/gpdb,randomtask1155/gpdb,Quikling/gpdb,rvs/gpdb,atris/gpdb,janebeckman/gpdb,zaksoup/gpdb,Chibin/gpdb,kaknikhil/gpdb,0x0FFF/gpdb,Quikling/gpdb,janebeckman/gpdb,lpetrov-pivotal/gpdb,ashwinstar/gpdb,lintzc/gpdb,lisakowen/gpdb,xuegang/gpdb,Chibin/gpdb,ashwinstar/gpdb,Quikling/gpdb,yuanzhao/gpdb,ashwinstar/gpdb,Chibin/gpdb,greenplum-db/gpdb,0x0FFF/gpdb,rvs/gpdb,royc1/gpdb,royc1/gpdb,atris/gpdb,rvs/gpdb,randomtask1155/gpdb,chrishajas/gpdb,lpetrov-pivotal/gpdb,chrishajas/gpdb,yuanzhao/gpdb,0x0FFF/gpdb,chrishajas/gpdb,xinzweb/gpdb,lisakowen/gpdb,greenplum-db/gpdb,cjcjameson/gpdb,royc1/gpdb,royc1/gpdb,foyzur/gpdb,Quikling/gpdb,Chibin/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,Chibin/gpdb,jmcatamney/gpdb,yuanzhao/gpdb,xuegang/gpdb,CraigHarris/gpdb,edespino/gpdb,foyzur/gpdb,CraigHarris/gpdb,edespino/gpdb,lpetrov-pivotal/gpdb,xinzweb/gpdb,cjcjameson/gpdb,atris/gpdb,cjcjameson/gpdb,adam8157/gpdb,edespino/gpdb,lisakowen/gpdb,foyzur/gpdb,cjcjameson/gpdb,50wu/gpdb,lisakowen/gpdb,kaknikhil/gpdb,rubikloud/gpdb,edespino/gpdb,0x0FFF/gpdb,atris/gpdb,Chibin/gpdb,xinzweb/gpdb,rvs/gpdb,lintzc/gpdb,cjcjameson/gpdb,lintzc/gpdb,0x0FFF/gpdb,lpetrov-pivotal/gpdb,50wu/gpdb,edespino/gpdb,foyzur/gpdb,ahachete/gpdb,kaknikhil/gpdb,randomtask1155/gpdb,Chibin/gpdb,xinzweb/gpdb,kaknikhil/gpdb,lintzc/gpdb,chrishajas/gpdb,greenplum-db/gpdb,tangp3/gpdb,adam8157/gpdb,ashwinstar/gpdb,janebeckman/gpdb,foyzur/gpdb,ahachete/gpdb,foyzur/gpdb,janebeckman/gpdb,ashwinstar/gpdb,ahachete/gpdb,yuanzhao/gpdb,greenplum-db/gpdb,50wu/gpdb,lpetrov-pivotal/gpdb,yuanzhao/gpdb,lpetrov-pivotal/gpdb,rubikloud/gpdb,cjcjameson/gpdb,xuegang/gpdb,ahachete/gpdb,janebeckman/gpdb,greenplum-db/gpdb,edespino/gpdb,greenplum-db/gpdb,lintzc/gpdb,Chibin/gpdb,jmcatamney/gpdb,cjcjameson/gpdb,randomtask1155/gpdb,lisakowen/gpdb,lintzc/gpdb,royc1/gpdb,CraigHarris/gpdb,lisakowen/gpdb,lpetrov-pivotal/gpdb,atris/gpdb,chrishajas/gpdb,xuegang/gpdb,50wu/gpdb,randomtask1155/gpdb,edespino/gpdb,zaksoup/gpdb,50wu/gpdb,ahachete/gpdb,atris/gpdb,xinzweb/gpdb,adam8157/gpdb,xuegang/gpdb,yuanzhao/gpdb,50wu/gpdb,lintzc/gpdb,atris/gpdb,edespino/gpdb,xuegang/gpdb,adam8157/gpdb,edespino/gpdb,Quikling/gpdb,adam8157/gpdb,ashwinstar/gpdb,ahachete/gpdb,rvs/gpdb,xuegang/gpdb,greenplum-db/gpdb,tangp3/gpdb,Quikling/gpdb,yuanzhao/gpdb,royc1/gpdb,50wu/gpdb,jmcatamney/gpdb,0x0FFF/gpdb,rvs/gpdb,randomtask1155/gpdb,lintzc/gpdb,ahachete/gpdb,cjcjameson/gpdb,janebeckman/gpdb,cjcjameson/gpdb,foyzur/gpdb,CraigHarris/gpdb,xinzweb/gpdb,jmcatamney/gpdb,janebeckman/gpdb,rubikloud/gpdb,jmcatamney/gpdb,zaksoup/gpdb,tangp3/gpdb,rubikloud/gpdb,kaknikhil/gpdb,CraigHarris/gpdb,jmcatamney/gpdb,ahachete/gpdb,lisakowen/gpdb,chrishajas/gpdb,kaknikhil/gpdb,kaknikhil/gpdb,xuegang/gpdb,rvs/gpdb,kaknikhil/gpdb,xinzweb/gpdb,atris/gpdb,janebeckman/gpdb,randomtask1155/gpdb,zaksoup/gpdb,adam8157/gpdb,CraigHarris/gpdb,ashwinstar/gpdb,yuanzhao/gpdb,rvs/gpdb