Allow keep alive connection when ws is off

This help improves performance.

confs/site/reverse-proxy.conf

@@ -17,6 +17,8 @@ location {{ url }} {% raw %}{{% endraw +%}
 	proxy_http_version 1.1;
 	proxy_set_header Upgrade $http_upgrade;
 	proxy_set_header Connection "Upgrade";
+			{% else %}
+	proxy_set_header Connection "";
 			{% endif %}
 			{% if headers != "" %}
 				{% for header in headers.split(";") +%}