Set status_url for zuul

This defaults to http://$fqdn - which for us isn't quite what we want.
The fqdn is zuul01.openstack.org - but the status page should use the
cname at zuul.openstack.org.

Change-Id: Iac5abbbc4b9469b1b7950fbd4cbc45ff96d64e62

manifests/site.pp

@@ -1192,6 +1192,7 @@ node /^ze\d+\.openstack\.org$/ {
     site_variables_yaml_file => $::project_config::zuul_site_variables_yaml,
     require                  => $::project_config::config_dir,
     statsd_host              => 'graphite.openstack.org',
+    status_url               => 'https://zuul.openstack.org',
   }
 
   class { '::zuul::executor': }