Set proxy_host_buffering to off

This fixes an issue with Jenkins, where jenkins-cli.jar API connections
would not work correctly behind nginx.

More information: https://support.cloudbees.com/hc/en-us/articles/360040999411--HTTP-full-duplex-channel-timeout-when-using-the-Jenkins-CLI

Change-Id: I87678f5aeb6ac819b2ef29c81b7eca8a97840404
diff --git a/templates/vhost.conf.j2 b/templates/vhost.conf.j2
index 121e33f..f5e7e8a 100644
--- a/templates/vhost.conf.j2
+++ b/templates/vhost.conf.j2
@@ -142,6 +142,7 @@
     proxy_http_version    1.1;
     proxy_read_timeout    60;
     proxy_connect_timeout 90;
+    proxy_request_buffering off;
 
     proxy_set_header      Host              $host;
     proxy_set_header      X-Forwarded-For   $proxy_add_x_forwarded_for;