Medium provider is not being loaded for Katello-managed hosts
The fix for discovery broke Katello: https://github.com/theforeman/foreman/commit/b15278e91ad1039803de7255385992aeca2d2f85, as it doesn't a 'medium' field but it's provided through the MediumProvider.
fixes #25007 - fix medium providers for plugins
Katello doesn't have medium set, since the medium is being provided
through the medium provider. This makes @medium_provider not load
and result in empty @kernel and @initrd in pxe templates.