Can we add a variable for server address(es) in all the upstreams too, now that this is decoupled from the app server.  I have something like:
    # For a TCP configuration:
    {% for app_server in app_servers %}
	server {{ app_server }}:{{ edxapp_lms_gunicorn_port }} fail_timeout=300;
	{% endfor %}
with a default app_server of 127.0.0.1?