Rackspace - Switch to CoreOS for standard cluster

The Rackspace setup for Kubernetes now leverages CoreOS instead of Ubuntu. We've dropped Salt completely for the cluster.

This doesn't include the updated release scripts so I've left those in the icebox for now.
Thanks for the info.

I was planning to do the swift release management in another PR once this was merged and working. Since there were some breaking changes just introduced, I can probably get that added in.

Ultimately, I wanted people to be able to choose if they want to deploy dev, a nightly or a versioned release easily.