Keep `cronjob` logs in `journald`

[simon-wacker]

We currently use journald for all logs but for the ones produced by cronjobs set up in the Ansible playbook local.yml. For those we used *.log files instead before f6998af. After that commit we just sent emails on errors. It would be nice to still send emails but also keep logs in jounald. Those logs can be searched, filtered, viewed, ... with journalctl. This is one point in #16