Import ntp 4.2.8 from meta-networking. Our version has some weird
dependency issues that create build breakages and more.
Remove the pps-tools dependency compared to meta-networking and
leave the ntp.conf as doneby Harald (e.g. drift on /etc and not
in /var...). Now I have not verified the upgrade path but I sadly
merged testing to stable when the ntp changes were comitted on
monday. This means I can't easily test the upgrade.