Added RadosGW support

Originally https://github.com/crowbar/barclamp-ceph/pull/55

Partially ported from upstream cookbook.
> If keystone is not deployed on this node, the recipe will not be executed

But this is still wrong: what we care about is keystone being deployed in this SUSE Cloud deployment.

> node[:keystone][:signing][:ca_certs] is by default /etc/keystone/ssl/certs/ca.pem, so why is it wrong?

But you're not using the `node[:keystone][:signing]` attributes here. Btw, you found a bug in barclamp-keystone where sometimes the path to these certificates are hard-coded instead of using the attributes :-)