Figure out why we need to delete related comments from NodeStorage::delete

Figure out why we need to delete related comments from NodeStorage::delete(). The core NodeStorage handler doesn't seem to need this (it's probably done via some hook somewhere). But for some reason that hook (or whatever other mechanism) doesn't seem to fire when using Multiversion's NodeStorage handler.

  /**
   * {@inheritdoc}
   *
   * @todo: {@link https://www.drupal.org/node/2597534 Figure out why we need
   * this}, core seems to solve it some other way.
   */
  public function delete(array $entities) {
    // Delete all comments before deleting the nodes.
    $comment_storage = \Drupal::entityManager()->getStorage('comment');
    foreach ($entities as $entity) {
      if ($entity->comment) {
        $comments = $comment_storage->loadThread($entity, 'comment', 1);
        $comment_storage->delete($comments);
      }
    }
    $this->deleteEntities($entities);
  }

Once this is figured out we should be able to remove the NodeStorage handler for good, since this is the last method we override in NodeStorage.