test/empty-eownerdead: Clarify unexpected error message
test/empty-eownerdead: Clarify unexpected error message

Old kernels incorrectly return EOWNERDEAD, catch that explicitly and
print a more clear error message to avoid unsuspecting users think
the test might be buggy, when it is the kernel.

Reword fallback error message too to make it clear these are unexpected
too.

Signed-off-by: Guillem Jover <6f269179bd29909dac5e2359bafef574d0759c09@hadrons.org>

axboe/liburing,axboe/liburing,axboe/liburing