Port RadosGW support from upstream cookbook.

Originally https://github.com/crowbar/barclamp-ceph/pull/55
> So we need to skip to 11, even if there's no migration from 3 to 9?

Yes. That's because we keep these values in case we need a schema change in roxy.

> Won't the schema-revision 10 pick everyting up to 10?

No.