Fix uWSGI configuration for clean shutdown

In absence of the exit-on-reload configuration option, uWSGI does not
exit cleanly when consul-template attempts to restart it. This manifests
as an error like: `bind(): Address already in use [core/socket.c line 769]`.
Fix the configuration appropriately.

docker/prod/uwsgi.ini

@@ -1,4 +1,6 @@
 [uwsgi]
+uid = www-data
+gid = www-data
 master = true
 http = 0.0.0.0:8080
 module = artwork_redirect.wsgi
@@ -9,3 +11,8 @@ processes = 10
 die-on-term = true
 worker-reload-mercy = 10
 reload-mercy = 25
+log-x-forwarded-for=true
+; quit uwsgi if the python app fails to load
+need-app = true
+; when uwsgi gets a sighup, quit completely and let runit restart us
+exit-on-reload = true