Updates required:
- Use vpc image format (new default, supported by Amazon)
- Pass full image filename to makeEc2Test
- Increase memory allocation for nixos-rebuild
- Set a networking.hostName for services.httpd
- Add appropriate escaping in literal userdata
While I'm here, try to make it fail fast.
The Openstack metadata service exposes the EC2 API. We use the
existing `ec2.nix` module to configure the hostname and ssh keys of an
Openstack Instance.
A test checks the ssh server is well configured.
This is mainly to reduce the size of the image (700MB). Also,
declarative features provided by cloud-init are not really useful
since we would prefer to use our `configuration.nix` file instead.
