title: kubernetes hpa issue with metrics-server
body: <p>I've configured a kubernetes cluster with metrics-server (as an aggregated apiserver) replacing heapster. kubectl top works fine, as do the raw endpoints in the metrics.k8s.io/v1beta1 api group. HPA, however, does not. controller-manager logs show the following errors (and no others):</p>
  
  <pre><code>E1008 10:45:18.462447       1 horizontal.go:188] failed to compute desired number of replicas based on listed metrics for Deployment/kube-system/nginx: failed to get cpu utilization: missing request for cpu on container nginx in pod kube-system/nginx-64f497f8fd-7kr96
  I1008 10:45:18.462511       1 event.go:221] Event(v1.ObjectReference{Kind:"HorizontalPodAutoscaler", Namespace:"kube-system", Name:"nginx", UID:"387f256e-cade-11e8-9cfa-525400c042d5", APIVersion:"autoscaling/v2beta1", ResourceVersion:"3367", FieldPath:""}): type: 'Warning' reason: 'FailedGetResourceMetric' missing request for cpu on container nginx in pod kube-system/nginx-64f497f8fd-7kr96
  I1008 10:45:18.462529       1 event.go:221] Event(v1.ObjectReference{Kind:"HorizontalPodAutoscaler", Namespace:"kube-system", Name:"nginx", UID:"387f256e-cade-11e8-9cfa-525400c042d5", APIVersion:"autoscaling/v2beta1", ResourceVersion:"3367", FieldPath:""}): type: 'Warning' reason: 'FailedComputeMetricsReplicas' failed to get cpu utilization: missing request for cpu on container nginx in pod kube-system/nginx-64f497f8fd-7kr96
  </code></pre>
  
  <p>metrics-server spec:</p>
  
  <pre><code>spec:
    containers:
    - args:
      - --kubelet-preferred-address-types=InternalIP
      image: k8s.gcr.io/metrics-server-amd64:v0.3.1
      imagePullPolicy: Always
      name: metrics-server
      resources: {}
      terminationMessagePath: /dev/termination-log
      terminationMessagePolicy: File
      volumeMounts:
      - mountPath: /tmp
        name: tmp-dir
    dnsPolicy: ClusterFirst
    restartPolicy: Always
    schedulerName: default-scheduler
    securityContext: {}
    serviceAccount: metrics-server
    serviceAccountName: metrics-server
    terminationGracePeriodSeconds: 30
    volumes:
    - emptyDir: {}
      name: tmp-dir
  </code></pre>
  
  <p>controller-manager is running with</p>
  
  <pre><code>--horizontal-pod-autoscaler-use-rest-clients="true"
  </code></pre>
  
  <p>k8s version 1.11.3</p>
  
  <p>Any ideas?</p>