Make sure the images tree is owned by www-data

This is mostly a belt-and-braces measure, as the images tree is
stateful and copied from deployment to deployment, but just in case
permissions on those files weren't set correctly when
copying/unpacking, have Puppet take care of correcting their
ownership.

Change-Id: Ib682e04e9f324f22ad4e1085946d8100949b0e3f

manifests/init.pp

@@ -54,6 +54,9 @@ class mediawiki(
 
     file { $mediawiki_images_location:
       ensure  => directory,
+      recurse => true,
+      owner   => 'www-data',
+      group   => 'www-data',
       require => File['/srv/mediawiki-data'],
     }