Bug: unattended_upgrades api test has an unstated dependency of being connected to AC power

[orndorffgrant]

Description of the bug

At least on noble, when run on a laptop that is not plugged in, features/api/unattended_upgrades.feature will fail when looking for a non-null last_run value. It fails because the unattended-upgrade will refuse to run when not connected to power.

Expected behavior

This test should either pass when not connected to power, or fail loudly with a clear explanation that it requires being connected to power.

Current behavior

The test fails when looking for a non-null value with no indication that it is not due to a bug.

To Reproduce

1. Unplug your laptop
2. tox run -e behave -- features/api/unattended_upgrades.feature -D releases=noble -D machine_types=lxd-container

[orndorffgrant]

There should be a configuration to tell unattended-upgrades to run even if not connected. We can hopefully just set that on before triggering it.

Unattended-Upgrade::OnlyOnACPower "false"