Move the current user out of the node API chain in book

Note that migrate_drupal runs migrate_drupal_module_implements_alter to nuke book_node_presave then copies it to migrate_drupal_node_presave with a killswitch:

function migrate_drupal_node_presave(EntityInterface $node) {
  // Always save a revision for non-administrators.
  if (empty($node->beingMigrated) && !empty($node->book['bid']) && !\Drupal::currentUser()->hasPermission('administer nodes')) {
    $node->setNewRevision();
// rest of book_node_presave follows.

this shouldn't be necessary.

I can confirm this solves the problem migrate faces; assigning to pwolanin for review.

Looks ok, though all the hook_node_X implementations should be using NodeInterface. I guess we can fix that in a follow-up.

3: book-2218691-3.patch queued for re-testing.

Back to RTBC after bot fluke.

Fixing tag so I can find this again once it's back from testbot.

un-assigning since the review is done

Committed/pushed to 8.x, thanks!