See clientside/tmcc/linux/docker/README.md for design notes.
See clientside/tmcc/linux/docker/dockerfiles/README.md for a description
of how we automatically Emulabize existing Docker images.

Also, this mostly fits within the existing vnodesetup path, but I did modify
mkvnode.pl to allow the libvnode backend to provide a vnodePoll wait
loop instead of the builtin vnodeState loop.