Commit b504810 introduced a NAT to make worker capable of reaching the
public internet via the provisioner.
But it also introduced a bug, it only works for the Vagrant setup as
Manny pointed out:
https://github.com/tinkerbell/sandbox/pull/33#issuecomment-759651035
This is an attempt to fix it
Signed-off-by: Gianluca Arbezzano <gianarb92@gmail.com>
