inotify is smart enough to notify you about any changes in a
directory, even if you only watch the directory, and none if its
contents: the recursive add_watch I added was unnecessary.
The only thing that matters here is the recursive status update on
directory deletion.
And scan() has to be called _before_ the deferred call is registered.
(race condition: depending on the times, the previous patch could
apparently fail on the provided test. It's not the case anymore.)
