When 'nullb setup' fails to detect something, e.g. the null_blk module,
the whole test fails though the failure is supposed to be caught and
test not run. Use the correct helper that handles potential failures.
Signed-off-by: David Sterba <dsterba@suse.com>
Create a few emulated zoned devices and run mkfs, the zone reset is
expected to be run in parallel. It's using memory-backed devices so it's
too fast to measure the differences and we can't expect availability of
slow zoned devices so this test is very simplistic.
Signed-off-by: David Sterba <dsterba@suse.com>