Fixes #6559: Net::DHCP classloading error

first option: is used in katello and in staypuft, `app/lib` is autoloaded and never required, `lib` is only required so it has not conflict between require and autoloading.

second option: is to find the problematic constant and use fully-quantified-name to avoid the load-order-collision.

Also do we have the original error? I may be looking at it wrong.