test: poll-mshot-overflow use proper return codes
test: poll-mshot-overflow use proper return codes

This missed out on the refactor, so do it now in preparation for adding a
skip path.

Signed-off-by: Dylan Yudaken <203ae8bb785c49229d9d2ff72bddc0c8f3aba6ea@fb.com>
Link: https://lore.kernel.org/r/20220721144229.1224141-4-203ae8bb785c49229d9d2ff72bddc0c8f3aba6ea@fb.com
Signed-off-by: Jens Axboe <cd8c6775e60d6f67a6984377324e5290df3d5358@kernel.dk>

axboe/liburing,axboe/liburing,axboe/liburing