server/grab: add test case for ungrab during second touch
server/grab: add test case for ungrab during second touch

This currently crashes the server, the listener is removed and triggers a
bug, replaying the event after the ungrab means accessing dangling pointers.

Signed-off-by: Peter Hutterer <b9c50af7afa7642f6f854434cda9ffe54ece8b85@who-t.net>

freedesktop-unofficial-mirror/xorg__test__xorg-integration-tests,freedesktop-unofficial-mirror/xorg__test__xorg-integration-tests,freedesktop-unofficial-mirror/xorg__test__xorg-integration-tests