tests: fix and improve nop tests
tests: fix and improve nop tests

We removed CQE32 for nops from the kernel, fix the tests and instead
test that we return zeroes in the extra fields instead of garbage.
Loop over the tests multiple times so it exhausts CQ and we also test
CQ entries recycling and internal caching mechanism. Also excersie
IOSQE_ASYNC.

Signed-off-by: Pavel Begunkov <8608d41fe50396a9dbd36e830be65ba791e26c05@gmail.com>
Link: https://lore.kernel.org/r/92f01041e5ef933a6018bd89dd54cc1fae57c6f6.1655455225.git.8608d41fe50396a9dbd36e830be65ba791e26c05@gmail.com
Signed-off-by: Jens Axboe <cd8c6775e60d6f67a6984377324e5290df3d5358@kernel.dk>

axboe/liburing,axboe/liburing,axboe/liburing