caddy-frontend: Keep connection to the backend

There is no reason to drop connection to the backend and then reinitate it on
each request. It's better to keep connected and avoid additional work,
especially in SSL handshake.

Note: This was kept as the file has been copied from other place (haproxy
      on a backend), and slipped MR review, where MR author wanted to drop it
      anyway.

software/caddy-frontend/buildout.hash.cfg

@@ -54,7 +54,7 @@ md5sum = 266f175dbdfc588af7a86b0b1884fe73
 
 [template-backend-haproxy-configuration]
 _update_hash_filename_ = templates/backend-haproxy.cfg.in
-md5sum = 8daeaaa02190d90e0df91e364b1d2fc0
+md5sum = 68a7758ca8f8b544ba9bc756824be3d3
 
 [template-log-access]
 _update_hash_filename_ = templates/template-log-access.conf.in

software/caddy-frontend/templates/backend-haproxy.cfg.in

@@ -13,8 +13,6 @@ defaults
   timeout client {{ configuration['request-timeout'] }}s
   timeout connect {{ configuration['backend-connect-timeout'] }}s
   retries {{ configuration['backend-connect-retries'] }}
-  # tentative below https://cbonte.github.io/haproxy-dconv/2.0/configuration.html#option%20httpclose
-  option httpclose
 
 {%- macro frontend_entry(slave_instance, scheme) %}
 {%-   set host_list = (slave_instance.get('server-alias') or  '').split() %}