aum-ota-auto: Use timedatectl to workaround NTP issues on some networks
With battery backed devices on networks with no properly reachable NTP servers
the boards would fail to automatically get the right time, so testers set it up
manually with date.
However, the hardware clock need to be configured as well for the time configuration to survive a reboot, needed by the Apertis update manager OTA test.
Without this, the device will fail to establish any TLS connection after the reboot since every certificate will look like they are out of their validity period.
This is only a workaround until we ensure NTP servers are reachable on the testers' network, see https://phabricator.apertis.org/T6115
Edited by Emanuele Aina