nbd: wait uninterruptible for the dead timeout

nbd: wait uninterruptible for the dead timeout

commit ff57dc94faec023abc267cdc45766fccff497557 upstream.

If we have a pending signal or the user kills their application then
it'll bring down the whole device, which is less than awesome.  Instead
wait uninterruptible for the dead timeout so we're sure we gave it our
best shot.

Fixes: 560bc4b39952 ("nbd: handle dead connections")
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>