rgw: BI Log updates can be missed during some OLH-related operations
It can happen when `rgw_cls_link_olh_op` carries explicitly set `olh_epoch` that is lower than the current `epoch` of the targeted OLH. However, `epoch` of the targeted object instance is actually changed. This may lead to divergences between bucket indexes in a multi-site arrangement.
Similar issue and under similar circumstances may when unlinking an object instance.