Ensure service is restarted on unit file changes

At the moment we don't restart services if systemd unit file is changed.

We knowingly prevent systemd_service role handlers to execute
by providing `state: started` as otherwise service will be restarted twice.
With that now  we ensure that role handlers will also listen for systemd
unit changes.

Change-Id: I3dcb02cfd8c5057411488dfefdd0b5381231a972

handlers/main.yml

@@ -26,6 +26,7 @@
   listen:
     - "Restart designate services"
     - "venv changed"
+    - "systemd service changed"
 
 - name: Perform Designate pools update
   command: "{{ designate_bin }}/designate-manage pool update --file /etc/designate/pools.yaml"
@@ -46,3 +47,4 @@
   listen:
     - "Restart designate services"
     - "venv changed"
+    - "systemd service changed"

vars/main.yml

@@ -29,7 +29,8 @@ filtered_designate_services: |-
   {%     set _ = value.update(
            {
              'service_key': key,
-             'enabled': 'yes',
+             'enabled': value['enabled'] | default(True),
+             'state': value['state'] | default('started'),
              'config_overrides': value.init_config_overrides
            }
          )