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: Ic56d5d1bd1ead8fd6bb642913370fa206799256f

handlers/main.yml

@@ -27,6 +27,7 @@
   listen:
     - "Restart aodh services"
     - "venv changed"
+    - "systemd service changed"
 
 - name: Start services
   service:
@@ -42,3 +43,4 @@
   listen:
     - "Restart aodh services"
     - "venv changed"
+    - "systemd service changed"

vars/main.yml

@@ -23,8 +23,8 @@ filtered_aodh_services: |-
   {%     set _ = value.update(
            {
              'service_key': key,
-             'enabled': 'yes',
-             'state': 'started',
+             'enabled': value['enabled'] | default(True),
+             'state': value['state'] | default('started'),
              'config_overrides': value.init_config_overrides
            }
          )