Clean up useless vars in prepare_plan_for_sharing
Clean up useless vars in prepare_plan_for_sharing

Remove xslice in prepare_plan_for_sharing, since it is always false.  cross
slice share type will be updated in function shareinput_mutator_xslice_2 and
shareinput_mutator_xslice_3.

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