Arvados

Feedback from #22238

• Install debootstrap and systemd-container before starting.
• Instead of checking for /etc/os-release, do a more explicit check to be sure the last debootstrap finished successfully.
  • Checking for /root/.ssh/ might work, that would not be created by debootstrap but should be created by the following task, even if /root/.ssh/authorized_keys is empty/removed later.
• Peter reported that ansible_user_id wasn't set. At the very least, pass that through the mandatory filter so it being unset is an error rather than a quiet noop. Worth investigating why this wasn't set too—Ansible facts should be pretty standardized.