Add handoffs_first and handoff_delete to obj-repl

If handoffs_first is True, then the object replicator will give
partitions that are not supposed to be on the node priority.

If handoff_delete is set to a number (n), then it will delete a handoff
partition if at least n replicas were successfully replicated

Also fixed a couple of things in the object replicator unit tests and
added some more

DocImpact

Change-Id: Icb9968953cf467be2a52046fb16f4b84eb5604e4
Merge "Add handoffs_first and handoff_delete to obj-repl"