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: I0265fc94d795360f6dfbddee5398ee067ea0422b

handlers/main.yml

@@ -30,6 +30,7 @@
   listen:
     - "Restart gnocchi services"
     - "venv changed"
+    - "systemd service changed"
 
 # Note (odyssey4me):
 # The policy.json file is currently read continually by the services
@@ -68,3 +69,4 @@
   listen:
     - "Restart gnocchi services"
     - "venv changed"
+    - "systemd service changed"

vars/main.yml

@@ -51,8 +51,8 @@ filtered_gnocchi_services: |-
   {%     set _ = service.update(
            {
              'service_key': name,
-             'enabled': 'yes',
-             'state': 'started',
+             'enabled': service['enabled'] | default(True),
+             'state': service['state'] | default('started'),
              'config_overrides': service.init_config_overrides
            }
          )