Also improve the assertion: check that qiov is NULL for other commands
than CMD_READ and CMD_WRITE.
Signed-off-by: NVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Message-Id: <20171012095319.136610-2-vsementsov@virtuozzo.com>
Signed-off-by: NEric Blake <eblake@redhat.com>