Nixops does not respect bootstrapImage field for GCE

[3noch]

This configuration absolutely refuses to use the bootstrap image that's specified. Instead it creates a new one from this derivation.

machine = {resources, ...}: {
    deployment.gce = credentials // {
      region         = "us-east1-b";
      instanceType   = "n1-standard-2";
      network        = resources.gceNetworks.build-net;

      bootstrapImage = "n-d55d7117915d11e6a1c6acbc32aa73f1-bootstrap";
      rootDiskType   = "ssd";
    };
}

[3noch]

This would be somewhat tolerable if it weren't for #536 and the fact that the 16.09 image for GCE appears to be down (unreachable). Hydra is down too, so perhaps that's why the image is unreachable. Thus I was trying to reuse an image that I had already successfully built from a previous deploy of a different derivation.