puppet/apache: Make the Apache user a virtual resource

This is required for appending the Apache user to groups later w/o hassle.

.vagrant-puppet/modules/apache/manifests/init.pp

@@ -35,7 +35,9 @@ class apache {
     require => Package['apache'],
   }
 
-  user { $user:
+  @user { $user:
     alias => 'apache',
   }
+
+  User <| alias == apache |>
 }