Bind v4 and v6 addresses separately in frontends

Use separate bind lines for IPv4 and IPv6.  Using "bind :::80 v4v6" causes
HAProxy to listen on v4 and v6 addresses but translate v4 source addresses
into v6 addresses, which can be seen in HTTP headers.  Using separate bind
lines causes HAProxy to report source addresses faithfully.

* images/router/haproxy/conf/haproxy-config.template: Use separate bind
lines for IPv4 and IPv6 listening addresses.

images/router/haproxy/conf/haproxy-config.template

@@ -163,7 +163,8 @@ listen stats
 {{ if .BindPorts -}}
 frontend public
     {{ if eq "v4v6" $router_ip_v4_v6_mode }}
-  bind :::{{env "ROUTER_SERVICE_HTTP_PORT" "80"}} v4v6
+  bind :{{env "ROUTER_SERVICE_HTTP_PORT" "80"}}
+  bind :::{{env "ROUTER_SERVICE_HTTP_PORT" "80"}} v6only
     {{- else if eq "v6" $router_ip_v4_v6_mode }}
   bind :::{{env "ROUTER_SERVICE_HTTP_PORT" "80"}} v6only
     {{- else }}
@@ -216,7 +217,8 @@ frontend public_ssl
   option tcplog
     {{- end }}
     {{ if eq "v4v6" $router_ip_v4_v6_mode }}
-  bind :::{{env "ROUTER_SERVICE_HTTPS_PORT" "443"}} v4v6
+  bind :{{env "ROUTER_SERVICE_HTTPS_PORT" "443"}}
+  bind :::{{env "ROUTER_SERVICE_HTTPS_PORT" "443"}} v6only
     {{- else if eq "v6" $router_ip_v4_v6_mode }}
   bind :::{{env "ROUTER_SERVICE_HTTPS_PORT" "443"}} v6only
     {{- else }}