Fixes #15721 - adapt rake tasks for host_uni and scoped search

[jlsherrill]

No description provided.

[jlsherrill]

Few notes:

• I discovered this while working on Fixes #12556 - remove System model #6187. This should fix that one last test (but likely will require a rebase).
• While the current tasks do not error, a lot of things are ignored/missed or not handled properly
• reimport (formally reindex), no longer tries to reimport systems/hosts as katello is the source of truth for all of those things.
• reindex used to use what is in the db as a basis for what should be in the backend services. Now reimport is mainly just importing things from backend systems and so really does not need to handle missing entities.

[daviddavis]

APJ