xwayland: Lock on entering surface if needed

When an X11 client issues a ConfinePointer wit ha hidden cursor,
Xwayland may translate that as a pointer lock.

However, if the pointer is located on another window at the time,
the request may be ignored, even if the pointer later enters the window.

To avoid that issue, check again if locking the pointer with a hidden
cursor is needed when pointer enters a surface.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Carlos Garnacho <carlosg@gnome.org>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>