ioengines: improve "is this the same IO engine" check

ioengines: improve "is this the same IO engine" check

We can't just compare the name, that assumes that name and filename
match for an IO engine. While that's generally the case for the
engines that fio ships with, it's not a requirement, and it's
definitely not true for external engines.

Fixup the check by re-loading the engine and checking the OPS
instead. That should be bullet proof.

Fixes: 800334d ("Correctly detect whether ioengine_load can exit early")
Signed-off-by: Jens Axboe <axboe@kernel.dk>