False positive for unused_preload_association

[darren987469]

I upgrade bullet from 5.7.5 to 5.9.0 and the following spec fail.

it 'should not detect unused preload associations' do
  comment = Comment.last
  post = Post.last
  comment.update(post: post)

  Bullet::Detector::UnusedEagerLoading.check_unused_preload_associations
  expect(Bullet::Detector::Association).not_to be_has_unused_preload_associations
end

After digging, it looks like the bug was introduced at 582b2d4b. In the spec, it misses the call check_unused_preload_associations and the spec fails. I opened a PR to show that #444.

[billgloff]

Also seeing the same behavior and have been on version 5.7.5 ever since last summer. Please look into merging the attached pr if it indeed fixes this issue. Thanks!