manifests/k8s: add service for discovering kube-dns metrics

The ports reflect the upstream kube-dns manifests of bootkube and
kubernetes/kubernetes.

manifests/k8s/kube-dns-bootkube-vagrant-multi.yaml

@@ -0,0 +1,20 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: kube-dns-prometheus-discovery
+  labels:
+    k8s-app: kube-dns
+spec:
+  selector:
+    k8s-app: kube-dns
+  type: ClusterIP
+  clusterIP: None
+  ports:
+  - name: prometheus-skydns
+    port: 10055
+    targetPort: 10055
+    protocol: TCP
+  - name: prometheus-dnsmasq
+    port: 10054
+    targetPort: 10054
+    protocol: TCP