We disable check-update.timer by default. Having a message in the
journal isn't helpful, and there currently is no API to properly
query for update (except for running swupd check-update).
We add auto-update timer units. These can be masked (`systemctl
mask swupd-update.service`) to disable auto-updates, or enabled
if the OS ships with them not enabled. The project ships with
them not enabled for now, may end up enabling them later in time.
Auke Kok