Add a new key=value label to controller nodes

* Add a node-role.kubernetes.io/controller="true" node label
to controllers so Prometheus service discovery can filter to
services that only run on controllers (i.e. masters)
* Leave node-role.kubernetes.io/master="" untouched as its
a Kubernetes convention

aws/container-linux/kubernetes/cl/controller.yaml.tmpl

@@ -81,6 +81,7 @@ systemd:
           --lock-file=/var/run/lock/kubelet.lock \
           --network-plugin=cni \
           --node-labels=node-role.kubernetes.io/master \
+          --node-labels=node-role.kubernetes.io/controller="true" \
           --pod-manifest-path=/etc/kubernetes/manifests \
           --register-with-taints=node-role.kubernetes.io/master=:NoSchedule \
           --volume-plugin-dir=/var/lib/kubelet/volumeplugins

bare-metal/container-linux/kubernetes/cl/controller.yaml.tmpl

@@ -90,6 +90,7 @@ systemd:
           --lock-file=/var/run/lock/kubelet.lock \
           --network-plugin=cni \
           --node-labels=node-role.kubernetes.io/master \
+          --node-labels=node-role.kubernetes.io/controller="true" \
           --pod-manifest-path=/etc/kubernetes/manifests \
           --register-with-taints=node-role.kubernetes.io/master=:NoSchedule \
           --volume-plugin-dir=/var/lib/kubelet/volumeplugins

digital-ocean/container-linux/kubernetes/cl/controller.yaml.tmpl

@@ -93,6 +93,7 @@ systemd:
           --lock-file=/var/run/lock/kubelet.lock \
           --network-plugin=cni \
           --node-labels=node-role.kubernetes.io/master \
+          --node-labels=node-role.kubernetes.io/controller="true" \
           --pod-manifest-path=/etc/kubernetes/manifests \
           --register-with-taints=node-role.kubernetes.io/master=:NoSchedule \
           --volume-plugin-dir=/var/lib/kubelet/volumeplugins

google-cloud/container-linux/kubernetes/controllers/cl/controller.yaml.tmpl

@@ -82,6 +82,7 @@ systemd:
           --lock-file=/var/run/lock/kubelet.lock \
           --network-plugin=cni \
           --node-labels=node-role.kubernetes.io/master \
+          --node-labels=node-role.kubernetes.io/controller="true" \
           --pod-manifest-path=/etc/kubernetes/manifests \
           --register-with-taints=node-role.kubernetes.io/master=:NoSchedule \
           --volume-plugin-dir=/var/lib/kubelet/volumeplugins