support soft reboots

[cgwalters]

We've invested in supporting systemd soft reboots in bootc.

tmt-reboot doesn't support this, and hence our tests can't.

[cgwalters]

See coreos/coreos-assembler#4119 where we added support in a different test framework.

EDIT: And I think coreos/coreos-assembler#4119 (comment) is equally relevant here.

[LecrisUT]

Could you also provide some context of why this is a needed feature so we can judge if we make it default or something else.

[cgwalters]

why this is a needed feature

Because we offer it as a feature to customers to update all of userspace (when there's no kernel changes) efficiently.

if we make it default

It definitely can't work to change all reboots to soft reboots as some use cases will want to change the kernel for example.

As is today it is effectively an opt-in and I think it needs to stay that way.

[LecrisUT]

Could you help document or review the details of that option? The relevant documentation source is
https://tmt.readthedocs.io/en/stable/stories/features.html#reboot-during-test

tmt/stories/features/reboot.fmf

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description: |