Switch "network.sh" to new "--net" Docker option
Switch "play.sh" to new "--net" Docker option
Be careful about making sure interfaces are up

With a more recent Ubuntu and Docker, network interfaces were getting
creating but not being brought up automatically.  So here are some extra
"up" commands to fix that.
Remember to bring the outside "eth0" interface up

Under a slightly older Ubuntu and Docker, the interface was coming up
automatically.  Now, not so much.