Since we contributed AsyncNotifier back to the upstream pyinotify
project, we'll be able, one day, to remove the ganeti version of that
code. For now we still need it to support older distributions, but
having a note about when we'll be able to remove it is nice.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>