ublk: merge stop_work and quiesce_work

Save some lines by merging stop_work and quiesce_work into nosrv_work,
which looks at the recovery flags and does the right thing when the "no
ublk server" condition is detected.

Signed-off-by: Uday Shankar <ushankar@purestorage.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20241007182419.3263186-4-ushankar@purestorage.com


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