Author: Fabio M. Di Nitto <fdinitto(a)redhat.com>
Date: 2015-02-28 (Sat, 28 Feb 2015)
[PMTUd] fix notification callback to add private data
this is necessary to identify the callback when driving multiple
knet instances within the same daemon.
Signed-off-by: Fabio M. Di Nitto <fdinitto(a)redhat.com>