absorb kdump

[cgwalters]

Right now RHELAH has kdump enabled by default. The way this works is via a system service that runs on boot.

Because we generate the default initramfs already on the compose side, there's no reason for us to not just generate the kdump initramfs too. (But doing this will exacerbate our already bad kernel/initramfs copying issues).

The reason to do this is that it's a waste of CPU to generate the kdump initramfs on boot, particularly for dynamic cloud environments.

[jlebon]

Closing in favour of coreos/fedora-coreos-tracker#622.