Federation: separate notion of zone-name & dns-suffix

We can put subdomains into hosted zones (for example,
foo.federation.example.com can be hosted in example.com)

By allowing sharing a common hosted zone, this means the user doesn't
have to do as much setup.

hack/verify-flags/known-flags.txt

@@ -505,6 +505,7 @@ service-address
 service-cidr
 service-cluster-ip-range
 service-dns-domain
+service-dns-suffix
 service-generator
 service-node-port-range
 service-node-ports