[must-gather]Add GMR file trigger support

The API services can only use the file trigger for GMR as apache
disables signal handling. This PR adds the file trigger config for
every server.
GMR can be triggered by

  oc exec  <service pod> -- touch /var/lib/nova

Optionally non apache based services produce GMR also via

  oc exec <service pod> -- kill -USR2 1

templates/nova.conf

@@ -309,3 +309,7 @@ user_domain_name = {{ .default_user_domain}}
 
 [upgrade_levels]
 compute = auto
+
+[oslo_reports]
+# api services need file based GMR trigger as apache disables signal handling
+file_event_handler=/var/lib/nova