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