Logging the whole journalctl output is not the best idea. Fortunately,
it does not work right now and fails with a traceback :)
This change adds a new log_stdout argument to utils.execute() and uses it in
the "logs" inspection collector.
Also do not log the logs while logging the collected data.
Change-Id: Ibc726ac2c4f5eb06c73ac4765bb400077b84a6cc