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.
we are about to have support for authentication tokens, which are just ascii strings and don't require htpasswd building.    What would you consider the cleanest way to pass those from kube-up to the master (for my benefit if I have to modify this code subsequently to use tokens)