Disable default site for cacti

The apache module places a default vhost to /var/www/html which
stops the rewrite to cacti from working. Disable this vhost.

Change-Id: Ib282dd506a5086cfca5c8400bf27cca10099f59d

modules/openstack_project/manifests/cacti.pp

@@ -14,6 +14,7 @@ class openstack_project::cacti (
   }
 
   class { '::apache':
+    default_vhost => false,
     mpm_module => 'prefork',
   }
   class { '::apache::mod::rewrite': }