* Improve handling of timeouts in tests
Make timeout handling in tests more transparent. Added a custom shell
driver that allows to define global timeout for commands in the config
file, and replaced for/sleep constructs with infinite loops that will be
eventually terminated by pytest-timeout plugin. Current timeouts taken
from last runs on Github CI with some extra headroom.
* test_supervisor_is_updated shouldn't be skipped if no update was needed
* Allow more time for system startup
* Allow even more time for system startup
