server/multihead: fix occasionally-failing zaphod screen crossing test
server/multihead: fix occasionally-failing zaphod screen crossing test

This test would fail every so-often if the pointer hits 0 or width-1,
depending on pointer acceleration kicking in. Avoid this by warping the
pointer to just next to the barrier and then definitely moving across it.

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