Remove unused LWLocks, left over from workfile manager rewrite.
Remove unused LWLocks, left over from workfile manager rewrite.

Commit f1ef3668a8 forgot to remove these.

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