The object reconstructor has a handoffs-only mode that is very useful
when a cluster requires rapid rebalancing, like when disks are nearing
fullness. This mode's goal is to remove handoff partitions from disks
without spending effort on primary partitions. The object replicator
has a similar mode, though it varies in some details.
This commit adds a handoffs-only mode to the account and container
replicators.
Change-Id: I588b151ee65ae49d204bd6bf58555504c15edf9f
Closes-Bug: 1668399
47fed6f2f9