digital-ocean: Run etcd cluster on-host, across controllers

* Run etcd peers with TLS across controller nodes
* Deprecate self-hosted-etcd on the Digital Ocean platform
* Distribute etcd TLS certificates as part of initial provisioning
* Check the status of etcd by running `systemctl status etcd-member`

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

@@ -1,6 +1,29 @@
 ---
 systemd:
   units:
+    - name: etcd-member.service
+      enable: true
+      dropins:
+        - name: 40-etcd-cluster.conf
+          contents: |
+            [Service]
+            Environment="ETCD_IMAGE_TAG=v3.2.0"
+            Environment="ETCD_NAME=${etcd_name}"
+            Environment="ETCD_ADVERTISE_CLIENT_URLS=https://${etcd_domain}:2379"
+            Environment="ETCD_INITIAL_ADVERTISE_PEER_URLS=https://${etcd_domain}:2380"
+            Environment="ETCD_LISTEN_CLIENT_URLS=https://0.0.0.0:2379"
+            Environment="ETCD_LISTEN_PEER_URLS=https://0.0.0.0:2380"
+            Environment="ETCD_INITIAL_CLUSTER=${etcd_initial_cluster}"
+            Environment="ETCD_STRICT_RECONFIG_CHECK=true"
+            Environment="ETCD_SSL_DIR=/etc/ssl/etcd"
+            Environment="ETCD_TRUSTED_CA_FILE=/etc/ssl/certs/etcd/server-ca.crt"
+            Environment="ETCD_CERT_FILE=/etc/ssl/certs/etcd/server.crt"
+            Environment="ETCD_KEY_FILE=/etc/ssl/certs/etcd/server.key"
+            Environment="ETCD_CLIENT_CERT_AUTH=true"
+            Environment="ETCD_PEER_TRUSTED_CA_FILE=/etc/ssl/certs/etcd/peer-ca.crt"
+            Environment="ETCD_PEER_CERT_FILE=/etc/ssl/certs/etcd/peer.crt"
+            Environment="ETCD_PEER_KEY_FILE=/etc/ssl/certs/etcd/peer.key"
+            Environment="ETCD_PEER_CLIENT_CERT_AUTH=true"
     - name: docker.service
       enable: true
     - name: locksmithd.service