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: I4273d2fbcbff3028e693e3274093c1afebdcfca2

handlers/main.yml

@@ -70,6 +70,7 @@
     - "Restart nova services"
     - "venv changed"
     - "cert installed"
+    - "systemd service changed"
 
 - name: Start services
   service:
@@ -86,3 +87,4 @@
     - "Restart nova services"
     - "venv changed"
     - "cert installed"
+    - "systemd service changed"

vars/main.yml

@@ -41,7 +41,14 @@ filtered_nova_services: |-
           (('condition' not in value) or
            ('condition' in value and value['condition'])) and
            not ('wsgi_app' in value and value['wsgi_app']) %}
-  {%     set _ = value.update({'service_key': key}) %}
+  {%     set _ = value.update(
+            {
+             'service_key': key,
+             'enabled': value['enabled'] | default(True),
+             'state': value['state'] | default('started')
+            }
+          )
+  %}
   {%     set _ = services.append(value) %}
   {%   endif %}
   {% endfor %}