Merge pull request #42065 from MrHohn/dns-autoscaler-1.1.0

Automatic merge from submit-queue (batch tested with PRs 42058, 41160, 42065, 42076, 39338)

Bump up dns-horizontal-autoscaler to 1.1.1

cluster-proportional-autoscaler 1.1.1 is releasing by kubernetes-incubator/cluster-proportional-autoscaler#26, also bump it up for dns-horizontal-autoscaler to introduce below features:
- Add PreventSinglePointFailure option in linear mode.
- Use protobufs for communication with apiserver.
- Support switching control mode on-the-fly.

Note:
The new entry `"preventSinglePointFailure":true` ensures kube-dns to have at least 2 replicas when there is more than one node. Mitigate the issue mentioned in #40063.

@bowei @thockin 

**Release note**:

```release-note
NONE
```

cluster/addons/dns-horizontal-autoscaler/dns-horizontal-autoscaler.yaml

@@ -32,7 +32,7 @@ spec:
     spec:
       containers:
       - name: autoscaler
-        image: gcr.io/google_containers/cluster-proportional-autoscaler-amd64:1.0.0
+        image: gcr.io/google_containers/cluster-proportional-autoscaler-amd64:1.1.1
         resources:
             requests:
                 cpu: "20m"
@@ -41,11 +41,10 @@ spec:
           - /cluster-proportional-autoscaler
           - --namespace=kube-system
           - --configmap=kube-dns-autoscaler
-          - --mode=linear
           # Should keep target in sync with cluster/addons/dns/kubedns-controller.yaml.base
           - --target=Deployment/kube-dns
           # When cluster is using large nodes(with more cores), "coresPerReplica" should dominate.
           # If using small nodes, "nodesPerReplica" should dominate.
-          - --default-params={"linear":{"coresPerReplica":256,"nodesPerReplica":16,"min":1}}
+          - --default-params={"linear":{"coresPerReplica":256,"nodesPerReplica":16,"preventSinglePointFailure":true}}
           - --logtostderr=true
           - --v=2