tests: use weston_compositor_exit

Use the proper function to exit instead of the libwayland one, to allow main
handle_exit() to be called.

This is just to unify the exit paths.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>
2 jobs for mr/exitcodes in 6 minutes and 26 seconds (queued for 1 minute and 59 seconds)
Status Job ID Name Coverage
  Build
passed #100292
build-native-autotools

00:04:00

passed #100293
build-native-meson

00:02:26