Automatically backup and restore Swift rings from the undercloud

Automatically backup and restore Swift rings from the undercloud

Swift rings created or updated on the overcloud nodes will now be
stored on the undercloud at the end of the deployment.  An
additional consistency check is executed before storing them,
ensuring all rings within the cluster are identical.

These rings will be retrieved (before Puppet runs) by every node
when an UPDATE is executed, and by doing this will be in a
consistent state across the cluster.

This makes it possible to add, remove or replace nodes in an
existing cluster without manual operator interaction.

Closes-Bug: 1609421
Depends-On: Ic3da38cffdd993c768bdb137c17d625dff1aa372
Change-Id: I758179182265da5160c06bb95f4c6258dc0edcd6