Comment 12 for bug 1401929

I mean that it is a big overreach to force image IDs to exist at template validation time. I've said this before, but a template may actually _create_ the images for later servers, and currently we don't support that.

I do like the idea of only validating parameters quite a bit more, as a user can choose not to use the "image exists" validator and it will happily start deploying expecting that some later process will create it.