rgw: fix rgw cache invalidation after unregister_watch() error

rgw: fix rgw cache invalidation after unregister_watch() error

When a metadata osd fails, an unregister_watch() error may occur,
resulting in an rgw cache invalidation.
By adding an unregister_done flag and when a register_watch() error ,
performing a reinit() operation again,
After the first reinit() failure, the register_watch() will be performed again

Fixes: https://tracker.ceph.com/issues/59217
Signed-off-by: lichaochao <lichaochao2_yewu@cmss.chinamobile.com>