There are long-standing issues with ntp start ordering w.r.t unbound
and being able to resolve DNS names. Things have moved on to
systemd-timesyncd anyway. Move the ntp start from the generic
locations to only apply to older distros, and use system-timesyncd on
Bionic. Update testing.
Change-Id: I664539f93242e2c68d0cb1cf95c260f3bc03550d