* add get_object
* allow extra headers passthrough on HEAD/metadata reqeusts
* expose (account|container|get_object)_ring properties
Pipeline propety access to the auto_create_account_prefix also allows us to
bypass the early exit on a container HEAD for auto_create_accounts if the
container-updater hasn't cycled yet.
Allow overriding of storage policy index.
This is something the reconciler will need so that it can GET from one
policy, PUT in another, and then DELETE from the first one again.
DocImpact
Implements: blueprint storage-policies
Change-Id: I9b287d15f2426022d669d1186c9e22dd8ca13fb9
8bec50838c