- Ensure the cache dir is added to the collection loader
  path, in order to allow linting a collection role against
  a module this collection is providing

- Add missing default collection path to the loader for ansible
  version prior 2.15.0.dev0, as done by ansible's
  _configure_collection_loader(). The only remaining difference
  is the missing handling of COLLECTIONS_SCAN_SYS_PATH.

See ansible/ansible-lint#2969 for
reference.

Signed-off-by: Arnaud Patard <apatard@hupstream.com>