Make sure apt-get doesn't prompt for config info

Installing mdadm for RAID on the ephemeral drives installs postfix, and
without this, it will prompt for how to configure. We don't care how, and we
don't want to bother the user.
Move the RAID config after package installation

We need mdadm to configure RAID, so we do the RAID config slightly later.
Update the example server config with correct ephemeral device names.
Remove a deprecated TODO