zbd: use zone_lock to lock a zone

zbd: use zone_lock to lock a zone

commit 6f0c608564c3 ("zbd: Avoid async I/O multi-job workload deadlock")
introduced io_u_quiesce() when it failed to lock a zone to avoid deadlock.
This situation can happen on the other locking place like
zbd_convert_to_open_zone(). Thus, introduce common helper "zone_lock" to
lock a zone.

Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Tested-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>