Bug: when deleting a child post and the "Move favorites to parent?" option is
set, the parent's has_active_children flag is not cleared.
`give_favorites_to_parent` moves the votes, and moving the votes has the
side effect of reloading the post (to get the new score). But reloading
the post wipes out the is_deleted_changed? flag, which is used by `update_parent_on_save`.
Fix: update the `is_deleted` flag *before* moving favorites, so that the
`update_parent_on_save` callback runs before `give_favorite_to_parent` runs.
acd49be4cc