main: absent packages should be purged

Mainly because this allows package removal to work properly on
RedHat-family, but also is good for cleaning up unused files on
Debian-family.

Author: kenyon

manifests/main.pp

@@ -1,7 +1,7 @@
 util::lookup_filter('classes').include
 
 ensure_packages(util::lookup_filter('packages'), { ensure => installed })
-ensure_packages(util::lookup_filter('packages_absent'), { ensure => absent })
+ensure_packages(util::lookup_filter('packages_absent'), { ensure => purged })
 
 lookup('files', Hash, 'hash', {}).each |$key, $value| {
   file { $key: