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.
When I tested this, it wasn't updating the minions very often. I do think it checks at some point but it certainly didn't seem to be "watching" the file. The sighup seems to work like charm.