Move docker systemd unit creation to docker role

Creating the unit using default settings early on
and then changing it during network_plugin section
leads to too many docker restarts and duplicated code.

Reversed Wants= dependence on docker.service so it does not
restart docker when reloading systemd

Consolidated all docker restart handlers.

roles/docker/handlers/main.yml

@@ -4,6 +4,8 @@
   notify:
     - Docker | reload systemd
     - Docker | reload docker
+    - Docker | pause while Docker restarts
+    - Docker | wait for docker
 
 - name : Docker | reload systemd
   shell: systemctl daemon-reload
@@ -13,3 +15,13 @@
   service:
     name: docker
     state: restarted
+
+- name: Docker | pause while Docker restarts
+  pause: seconds=10 prompt="Waiting for docker restart"
+
+- name: Docker | wait for docker
+  command: /usr/bin/docker images
+  register: docker_ready
+  retries: 10
+  delay: 5
+  until: docker_ready.rc == 0