t/zbd: check for error in test #2

t/zbd: check for error in test #2

With the preceding commit in place, fio gives an error if user attempts
to run write I/O size that is larger than the zone size. Grep for that
message instead of checking that no write has happened.

Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
Reviewed-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>