Host creation form bounces from synced content to media not found
The Host::Managed media validator has always been overridden by Katello, as Synced content does not need installation media to work.
Check out the following gif for an example:
The problem is that https://github.com/Katello/katello/commit/a32a9be522015a1ef925038ca2cf94722efb6307#diff-4a41cc0011db848f8d1bc5025f997d12R9 renamed the override from "validate_media?" to "validate_media" (no question mark).
Renaming that and adding some tests to ensure hosts with synced content.