Comment 4 for bug 1760128

There is a workaround for this bug, which I found at:
https://neklaf.wordpress.com/2015/04/02/workaround-to-debian-gnulinux-upgrade/
where you manually disable avahi-daemon before the dpkg operation and reenable it afterwards:

1. sudo systemctl disable avahi-daemon
2. (upgrade/reinstall avahi-dnsconfd)
3. sudo systemctl enable avahi-daemon

This worked for me on 16.04.4.