Fix notification dbus bug

The real problem is described here [1], and this workaround can be
safely removed after that patch lands our notification-daemon's
debian package. It's worth to investigate whether we're going to
receive this patch as an update of our base distro, either from
Debian, Ubuntu or Mint.

[1] https://bugzilla.gnome.org/show_bug.cgi?id=728157

BTW, here's the report against debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=747465
As you can see, the workaround we're using does not prevent the notification-daemon from crashing, it just keeps the notification-daemon alive (by restarting it) after a crash. That's the reason we would like to include the real patch provided upstream: https://bugzilla.gnome.org/attachment.cgi?id=288082