mount os-release to ensure the node's OS is what's seen in k8s api

roles/kubernetes/node/templates/kubelet-container.j2

@@ -25,6 +25,7 @@
   -v /var/lib/cni:/var/lib/cni:shared \
   -v /var/run:/var/run:rw \
   -v {{kube_config_dir}}:{{kube_config_dir}}:ro \
+  -v /etc/os-release:/etc/os-release \
   {{ hyperkube_image_repo }}:{{ hyperkube_image_tag}} \
   ./hyperkube kubelet \
   "$@"