fixed: deprecated variables access

fixes flooding with log warnings like these:
Jan 26 03:37:21 edeaclx0664 puppet-master[19494]: Variable access via 'preamble' is deprecated. Use '@preamble' instead. template[/etc/puppet/deac_modules/sudoers/templates/sudoers.erb]:6
Jan 26 03:37:21 edeaclx0664 puppet-master[19494]: Variable access via 'rules' is deprecated. Use '@rules' instead. template[/etc/puppet/deac_modules/sudoers/templates/sudoers.erb]:7