Partial revert of 421934e

Keeping the server block of websocket definitions but also bringing back the
location block after discussions on #1067

backend/templates/proxy_host.conf

@@ -53,6 +53,12 @@ proxy_http_version 1.1;
 
 {% include "_hsts.conf" %}
 
+    {% if allow_websocket_upgrade == 1 or allow_websocket_upgrade == true %}
+    proxy_set_header Upgrade $http_upgrade;
+    proxy_set_header Connection $http_connection;
+    proxy_http_version 1.1;
+    {% endif %}
+
     # Proxy!
     include conf.d/include/proxy.conf;
   }