Pure Storage support for sync-rep for Cinder

Pure Storage FlashArray devices are now able to use synchronous replication via the ActiveCluster feature in Purity. Support for this should be added to the existing async replication capabilities in the Volume drivers.

Configure the Cinder image-volume cache by default for devstack

The generic image-volume cache for Cinder has been around for a couple of releases now and should be pushed as the standard way to configure and deploy Cinder (for nearly all backends). A step towards that goal is to configure and enable it in devstack so that it gets significantly more test coverage and there is an...

Add a pure cinder_backend to configure PureISCSIDriver for devstack

We should have support in DevStack to allow for more automatically configuring the PureISCSIDriver for Cinder. This will make it easier for us to configure our 3rd party CI, get developers set up, and let others try out OpenStack with our Flash Array. A reach goal for this is to have it be able to configure multipa...