Further explanation.
Do *not* ssh as root.

The appliance-security branch disables root logins via ssh. Rather than trying
to play cat and mouse and re-enable it, let's play by the rules and set up our
tunnel as a non-root user.

The basic vest options have been tested, eg. `vest -v <machine> -r <branch>`
and `vest -v <machine> -u <branch>`, without error.