Don't alter NodeStatus in DetailsDocumentWriter.
The following two things went wrong when splitting up NodeDataWriter into two classes in e152b676: - Writing exit addresses to details documents doesn't require adding these addresses to the NodeStatus instance only to filter out known OR addresses. That's something we can also do in DetailsDocumentWriter. - Writing details documents is not the right place to learn the latest contact line of a relay to update our NodeStatus. This is something we can do when parsing the relay descriptor in NodeDetailsStatusUpdater. These are no bugs, but things that make it harder to refactor DetailsDocumentWriter.