Automatic merge from submit-queue

federation: choosing a default federation name in test instead of failing

The tests are failing right now:
http://kubekins.dls.corp.google.com/job/kubernetes-e2e-gce-federation/

```
[k8s.io] Service [Feature:Federation] should be able to discover a non-local federated service

/go/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/test/e2e/federated-service.go:130 Jun 14 12:40:35.091: FEDERATION_NAME environment variable must be set


[k8s.io] Service [Feature:Federation] should be able to discover a federated service

/go/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/test/e2e/federated-service.go:130 Jun 14 12:40:40.802: FEDERATION_NAME environment variable must be set
```

This is to fix them.

cc @kubernetes/sig-cluster-federation @mml