Nomad on the packer image will be overwritten by the sha specified in
the TF var, but including a base version on the packer image makes the
image valid for independent use.
The systemd configs spread across our repo were fairly out of sync. This
should get them on our best practices.
The deployment guide also had some strange things like running Nomad as
a non-root user. It would be fine for servers but completely breaks
clients. For simplicity I simply removed the non-root user references.
