Rails 5 introduced a new (and safer) autoload mechanism which
uses locking when loading missing constants. Under some circumstances
it's possible that a deadlock occurs in multi-threaded environment
(especially when running capybara tests)

To avoid these deadlocks, concurrent load is enabled when loading
policies - we ere hitting timeout in this case:
https://gitlab.com/gitlab-org/gitlab-ce/issues/48263

Note that autoloading is enabled only in development or test envs
(not in production).