nbd: fix order of cleaning up the queue and freeing the tagset

We must release the queue before freeing the tagset.

Fixes: 4af5f2e0 ("nbd: use blk_mq_alloc_disk and blk_cleanup_disk")
Reported-and-tested-by:  <syzbot+9ca43ff47167c0ee3466@syzkaller.appspotmail.com>
Signed-off-by: Wang Qing <wangqing@vivo.com>
Signed-off-by: Guoqing Jiang <jiangguoqing@kylinos.cn>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210706040016.1360412-1-guoqing.jiang@linux.dev


Signed-off-by: Jens Axboe <axboe@kernel.dk>