/usr/lib/systemd/system/avahi-daemon.service expects itself a Type=dbus unit. Without USE=dbus, `systemctl start avahi-daemon.service' will hang (stuck at systemd-tty-ask-password-agent --watch) and timeout. Dec 26 12:33:55 localvm systemd[1]: avahi-daemon.service: Start operation timed out. Terminating. Dec 26 12:33:55 localvm avahi-daemon[3011]: Got SIGTERM, quitting.
Please test avahi-0.7-r3. I added both a systemd and dbus flag, with dbus required with systemd. Reopen this bug if it doesn't work.