compositor: fix event-test

compositor: fix event-test

event-test assumes, that even without the very first wl_surface.attach
(and commit), the surface will have infinite (previously undef) input
region. event-test simply has test-client to create a wl_surface, and
then it forcefully sets its position and size, and assumes the input
region is now the full surface, so that notify_motion() will hit it.

Change Weston to initialize the input region to infinite, instead of
empty.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>