Clean up the deleted object after a period of time if the object is not marked deleted by all ESS

[LiilyZhang]

When object is deleted from CSS, the object status is "objectdeleted" until all related ESS mark delete for this object. If the object is not mark deleted by all the related ESS, its metadata is always shows in CSS. Need to clean up those after passing a certain time

[dabooz]

Today, you accomplish this by deleting the object a second time. This will remove all record of it from the hub (CSS). A timer based garbage collection function is a new feature.