Add missing configuration for cert renewal

Production/docker-compose.yml

@@ -45,6 +45,7 @@ services:
       - "nginx_certs:/etc/nginx/certs:rw"
     environment:
       NGINX_DOCKER_GEN_CONTAINER: "nginx-gen"
+      NGINX_PROXY_CONTAINER: "nginx"
       ACME_CA_URI:
     links:
       - nginx