Automatic merge from submit-queue (batch tested with PRs 37092, 37850)

Turns on dns horizontal scaling tests for GKE

Seems like the dns-autoscaler is already enabled in [this recent gke build](https://k8s-gubernator.appspot.com/build/kubernetes-jenkins/logs/ci-kubernetes-e2e-gci-gke/769/).
Turning on the corresponding e2e tests to increase test coverage.

Probably better to wait for this fix #37261 to go in first.

@bowei @bprashanth 
cc @maisem @roberthbailey