Add Celluloid reset back to spec runs for Ridley

Since Celluloid is still a dependency of Ridley, it should still be
shutdown and booted before each test to ensure there are no orphaned
threads.

Acked-by: Jamie Winsor <jamie@vialstudios.com>
Signed-off-by: Evan Owen <kainosnoema@gmail.com>
Remove CachedCookbook::loaded to hide internal implementation

We're not using this getter yet, and the fact that cached cookbooks
are loaded and stored on the class doesn't need to be exposed (yet).

Acked-by: Jamie Winsor <jamie@vialstudios.com>
Signed-off-by: Evan Owen <kainosnoema@gmail.com>