fix failed to create bucket if a non-master zonegroup has a single zone
If a non-master zonegroup has a single zone, the metadata sync thread not running and
the non-master zonegroup can't sync user from master zonegroup,
so we can't create bucket(or other metadata update) in it
because the authenticated user not found in the zone of non-master zonegroup.
The fix has been merged in kraken (https://github.com/ceph/ceph/pull/10991), We should backport for jewel