Use k8s.gcr.io instead of gcr.io/google_containers

* Kubernetes recommends using the alias to fetch images
from the nearest GCR regional mirror, to abstract the use
of GCR, and to drop names containing 'google'
* https://groups.google.com/forum/#!msg/kubernetes-dev/ytjk_rNrTa0/3EFUHvovCAAJ

digital-ocean/container-linux/kubernetes/bootkube.tf

@@ -1,6 +1,6 @@
 # Self-hosted Kubernetes assets (kubeconfig, manifests)
 module "bootkube" {
-  source = "git::https://github.com/poseidon/terraform-render-bootkube.git?ref=b408d80c593cef46aac49bd98c02dac9c7d7b7d8"
+  source = "git::https://github.com/poseidon/terraform-render-bootkube.git?ref=33e00a6dc5cdf2744b0f607329c1566ae8e5fde9"
 
   cluster_name          = "${var.cluster_name}"
   api_servers           = ["${format("%s.%s", var.cluster_name, var.dns_zone)}"]

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

@@ -123,7 +123,7 @@ storage:
       mode: 0644
       contents:
         inline: |
-          KUBELET_IMAGE_URL=docker://gcr.io/google_containers/hyperkube
+          KUBELET_IMAGE_URL=docker://k8s.gcr.io/hyperkube
           KUBELET_IMAGE_TAG=v1.10.0
     - path: /etc/sysctl.d/max-user-watches.conf
       filesystem: root

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

@@ -95,7 +95,7 @@ storage:
       mode: 0644
       contents:
         inline: |
-          KUBELET_IMAGE_URL=docker://gcr.io/google_containers/hyperkube
+          KUBELET_IMAGE_URL=docker://k8s.gcr.io/hyperkube
           KUBELET_IMAGE_TAG=v1.10.0
     - path: /etc/sysctl.d/max-user-watches.conf
       filesystem: root
@@ -114,7 +114,7 @@ storage:
             --volume config,kind=host,source=/etc/kubernetes \
             --mount volume=config,target=/etc/kubernetes \
             --insecure-options=image \
-            docker://gcr.io/google_containers/hyperkube:v1.10.0 \
+            docker://k8s.gcr.io/hyperkube:v1.10.0 \
             --net=host \
             --dns=host \
             --exec=/kubectl -- --kubeconfig=/etc/kubernetes/kubeconfig delete node $(hostname)