manifests: add headless services for k8s components

This way they are discoverable via the kubernetes endpoints discovery of
Prometheus.

manifests/k8s/kube-controller-manager-bootkube-vagrant-multi.yaml

@@ -0,0 +1,18 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: kube-controller-manager-prometheus-discovery
+  labels:
+    k8s-app: kube-controller-manager
+  annotations:
+    prometheus.io/scrape: 'true'
+spec:
+  selector:
+    k8s-app: kube-controller-manager
+  type: ClusterIP
+  clusterIP: None
+  ports:
+  - name: prometheus
+    port: 10252
+    targetPort: 10252
+    protocol: TCP