Secure the API listener

[JulienBalestra]

In CI, we set the listener to 0.0.0.0:8989:

script:
  - sudo ./pupernetes daemon run sandbox/ --job-type systemd --bind-address 0.0.0.0:8989 --hyperkube-version $HYPERKUBE_VERSION
  - ./.ci/pupernetes-validation.sh

This open the http server insecurely.