haproxy template: remove the port from the Host.

templates/haproxy.cfg.j2

@@ -142,6 +142,8 @@ frontend http
     option forwardfor
     # HSTS (63072000 seconds)
     http-response set-header Strict-Transport-Security max-age=63072000
+    # Remove the port from the host endpoint.
+    http-request replace-value Host (.*):.* \1
 {% if docker_swarm_cluster_portainer_install %}
     acl portainer_srv hdr(host) -i {{ docker_swarm_portainer_hostname }}
 {% endif %}