Enable access to HAProxy stats page

Enable access to the HAProxy stats page. The listen directive is bound
to the controller virtual IP address.

Change-Id: Ie0012da77ffdd9bfa8f06341aca2d70991558a28

manifests/loadbalancer.pp

@@ -242,11 +242,11 @@ class tripleo::loadbalancer (
   }
 
   haproxy::listen { 'haproxy.stats':
-    ipaddress        => '*',
+    ipaddress        => $controller_virtual_ip,
     ports            => '1993',
     mode             => 'http',
     options          => {
-      'stats' => 'enable',
+      'stats' => ['enable', 'uri /'],
     },
     collect_exported => false,
   }