Add optional deployment mode for Docker etcd_deployment_type

Running etcd in Docker reduces the number of individual file
downloads and services running on the host.

Note: etcd container v3.0.1 moves bindir to /usr/local/bin

Fixes: #298

roles/etcd/tasks/main.yml

@@ -8,7 +8,7 @@
 - name: Restart etcd if binary changed
   command: /bin/true
   notify: restart etcd
-  when: etcd_copy.stdout_lines
+  when: etcd_deployment_type == "host" and etcd_copy.stdout_lines
 
 # Reload systemd before starting service
 - meta: flush_handlers