Added RadosGW support

Originally https://github.com/crowbar/barclamp-ceph/pull/55

Partially ported from upstream cookbook.
> Could you point to such place where we have it?

https://github.com/crowbar/barclamp-keystone/blob/master/chef/cookbooks/keystone/recipes/server.rb#L503

> Otherwise, could we scp them? Or is it possible that we could not reach that server?

By default, nodes cannot ssh into each other :/ (it's only possible when HA is enabled, iirc)