Adds a retry mechanism when deleting containers

Bulk middleware now has a mechanism to retry a delete when the
HTTP response code is 409. This happens when the container still
has objects. It can be useful in a bulk delete where you delete
all the objects in a container and then try to delete the container.
It is very likely that at the end it will fail because the replica
objects have not been deleted by the time the middleware got a
successful response.

Change-Id: I1614fcb5cc511be26a9dda90753dd08ec9546a3c
Closes-Bug: #1253478
Refactor to share on-disk layout with hash cleanup

Closes-Bug: 1260132
Change-Id: Iaa367c686b8dc49dd53c55a7cca661d9611044f8
Merge "Adds a retry mechanism when deleting containers"
Merge "Refactor to share on-disk layout with hash cleanup"