[RFE] Create demo running docker run in unprivileged containers

[rata]

LXD has a very nice demo running docker inside a LXD container: https://www.youtube.com/watch?v=_fCSSEyiGro

I understand they use seccomp notify for mknod and other things docker uses.

@alban suggested we do a similar demo: a docker daemon running a Kubernetes pod without too many privileges, so that the user can just run docker run from inside the pod without giving CAP_SYS_ADMIN.

Once Flatcar adds supports for this, we should be able to create such demo. Upstream flatcar issue tracking support for this: flatcar/Flatcar#499