bundles/icinga2: only include service_name in sms if it actually is a service

bundles/icinga2/files/scripts/icinga_notification_wrapper

@@ -60,9 +60,9 @@ def log_to_syslog(message):
 
 def notify_per_sms():
     message = {
-        'message': 'ICINGA: {host}/{service} is {state}: {output}'.format(
+        'message': 'ICINGA: {host}{service} is {state}: {output}'.format(
             host=args.host_name,
-            service=args.service_name,
+            service=('/'+args.service_name if args.service_name else ''),
             state=args.state.upper(),
             output=args.output
         ),