Fixes #36844 - Fail early when syncing non-library repos

[sjha4]

What are the changes introduced in this pull request?

Fail properly when trying to sync non-library repos

Considerations taken when implementing this change?

What are the testing steps for this pull request?

1. Create a repository. (Note repo_id)
2. Add it to some CV and publish.
3. Fetch either the archived or the cv-env version repo from console. Katello::Repository.where(library_instance_id: repo_id).first
4. Try to sync the repo from step 3 using hammer: hammer repository sync --id=env_repo_id

[chris1984]

ACK, code looks fine and works well:

[vagrant@hammer ~]$ hammer repository sync --id=9
Could not synchronize the repository:
  attempted to sync a non-library repository.