Xe-toolstack-restart Fails with Error "Cannot Lock /dev/shm/xe_toolstack_restart.lock. Is an Instance of /opt/xensource/bin/xe-toolstack-restart Running Already? "

When trying to restart toolstack, following error is displayed: "cannot lock /dev/shm/xetoolstackrestart.lock. Is an instance of /opt/xensource/bin/xe-toolstack-restart running already? "...