Conformance test: DNS

[skitt]

https://github.com/kubernetes/enhancements/blob/master/keps/sig-multicluster/1645-multi-cluster-services-api/README.md#dns

Check that:

• [ ] Exported services are accessible using service.ns.svc.clusterset.local
• [ ] Headless services are represented by multiple A/AAAA records
• [ ] SRV records are available
• [ ] Headless services’ individual pods are accessible through hostname.clusterid.svc.ns.svc.clusterset.local
• [ ] The cluster.local zone is unchanged, and accessing services there only accesses local services
• [ ] Since .clusterset.local may be customized, the tests should allow it to be overridden

[tpantelis]

/assign @tpantelis