We now make it happen later in the boot process so that multi-user
has already activated, so as to not run afoul of the logic in
switch-to-configuration.pl. It's not my favorite solution, but at
least it works. Also added a check to the VM test to catch the failure
so we don't break in future.
Fixes#23121
We now generate a qcow2 image to prevent hitting Hydra's output size
limit. Also updated /root/user-data -> /etc/ec2-metadata/user-data.
http://hydra.nixos.org/build/33843133
