-ignore unmatched NACK/ACKs

git-svn-id: https://gnunet.org/svn/gnunet@31268 140774ce-b5e7-0310-ab8b-a85725594a96
-fix distance

git-svn-id: https://gnunet.org/svn/gnunet@31269 140774ce-b5e7-0310-ab8b-a85725594a96
-fix #3192, as suggested

git-svn-id: https://gnunet.org/svn/gnunet@31270 140774ce-b5e7-0310-ab8b-a85725594a96