Update RBAC settings for the metrics server

What does this commit/MR/PR do?

- Update RBAC settings for the metrics server

Why is this commit/MR/PR needed?

- Due to a bug, output below

```
error while getting metrics summary from Kubelet
amd64-node-1(10.1.244.207:10250): request failed - "403 Forbidden",
response: "Forbidden
(user=system:serviceaccount:kube-system:metrics-server, verb=get,
resource=nodes, subresource=stats)"
```

- Ref issue
`kubernetes-sigs/metrics-server#77

addons/metrics-server-rbac.yaml

@@ -63,6 +63,13 @@ rules:
   - get
   - list
   - watch
+- apiGroups:
+  - ""
+  resources:
+  - nodes/stats
+  verbs:
+  - get
+  - create
 ---
 apiVersion: rbac.authorization.k8s.io/v1
 kind: ClusterRoleBinding