metadata: name attribute is required in berkshelf >= 3.0.0

This small change enables the use of your `rpmbuild` cookbook with the current release of Berkshelf, fixing an error that looks like this:

    Ridley::Errors::MissingNameAttribute The metadata at '/tmp/d20140507-1685-n7imbz' does not contain a 'name' attribute. While Chef does not strictly enforce this requirement, Ridley cannot continue without a valid metadata 'name' entry.