[FC-35973] systemd timers non-persistent by default

[PhilTaken]

Systemd Timers were persistent by default previously. Since that implies a trigger on first activation, this is unwanted behaviour for Jobs that interact with the outside world, e.g. sending out emails.

The old behaviour can be enabled optionally. Looking over some uses of this Component in our deployments, I did not find any that rely on the old behaviour or ones that would not work with the new default.

[zagy]

@PhilTaken this is still draft, why?

[PhilTaken]

@PhilTaken this is still draft, why?

In testing I could not confirm the initial suspicion and as it turns out, persistence is not related to the problem at all.

We can still merge this but the problem is unrelated.