Fix backend config resource

It was causing a dependency cycle.

This resolves the issue by rearranging the
dependency.

manifests/api.pp

@@ -66,7 +66,7 @@ class glance::api(
     owner   => 'glance',
     group   => 'root',
     mode    => 640,
-    require => [Class['glance'], Glance::Api::Config['backend']],
+    require => Class['glance'],
   }
 
   glance::api::config { 'header':
@@ -88,8 +88,10 @@ class glance::api(
     config => {
       'auth_type' => $auth_type
     },
-    order  => '99'
+    order   => '99',
+    require => Glance::Api::Config['backend'],
   }
+
   file { '/etc/glance/glance-api-paste.ini':
     content => template('glance/glance-api-paste.ini.erb'),
   }