Ensure /etc/kubernetes exists following Kubelet inlining

* Inlining the Kubelet service removed the need for the
kubelet.env file declared in Ignition. However, on some
platforms, this removed the guarantee that /etc/kubernetes
exists. Bare-Metal and DigitalOcean distribute the kubelet
kubeconfig through Terraform file provisioner (scp) and
place it in (now missing) /etc/kubernetes
* poseidon/typhoon#606
* Fix bare-metal and DigitalOcean Ignition to ensure the
desired directory exists following first boot from disk
* Cloud platforms with worker pools distribute the kubeconfig
through Ignition user data (no impact or need)

cl/controller.yaml

@@ -152,6 +152,9 @@ systemd:
         [Install]
         WantedBy=multi-user.target
 storage:
+  directories:
+    - path: /etc/kubernetes
+      filesystem: root
   files:
     - path: /opt/bootstrap/layout
       filesystem: root

cl/worker.yaml

@@ -111,6 +111,9 @@ systemd:
         [Install]
         WantedBy=multi-user.target
 storage:
+  directories:
+    - path: /etc/kubernetes
+      filesystem: root
   files:
     - path: /etc/sysctl.d/max-user-watches.conf
       filesystem: root