Serve Katello api documentation on '/apidoc` when Katello is loaded

We use the foreman `/apidoc` path to serve the Katello's resources
when the engine is loaded. This allows both Katello and Foreman
to use apipie for their bindings without affecting each other.

There are some issues with loaded the Katello code when loading
apidoc. One of the possible fixes is commenting out `wrap_parameters`
call in Foreman's `config/initializers/wrap_parameters.rb` file.
When doing that, http://localhost:3000/apidoc will serve as the
Katello's original apidoc path, using the api docs from the engine
Merge pull request #3477 from iNecas/katello-apipie

Serve Katello api documentation on '/apidoc` when Katello is loaded