Improve logging

Currently its almost impossible to know which host actually handled the request, this extra variable logs the upstream server too

nginx.tmpl

@@ -108,7 +108,8 @@ gzip_types text/plain text/css application/javascript application/json applicati
 
 log_format vhost '$host $remote_addr - $remote_user [$time_local] '
                  '"$request" $status $body_bytes_sent '
-                 '"$http_referer" "$http_user_agent"';
+                 '"$http_referer" "$http_user_agent" '
+		 '"$upstream_addr"';
 
 access_log off;