Add test for Apertis update manager

Add a test to exercise the features of the Apertis update manager.
These tests only works on OSTree images and check following:
- API of update manager with `updatectl` utility
- automatic update from mass storage device with static delta
- manual upgrade with static delta file
- automatic rollback from "failed" update
- blacklist feature
- rollback feature of U-Boot bootloader

Signed-off-by: Frédéric Dalleau <frederic.dalleau@collabora.com>
Signed-off-by: Denis Pynkin <denis.pynkin@collabora.com>