Change UUID on first boot

[Anders Ingemann <anders@ingemann.de>]

I had the idea of creating a startup script which changes the UUID of
the root volume on first boot.
I create an issue on github:
https://github.com/andsens/ec2debian-build-ami/issues/40
Some of you might not have a github account, so I thought I would take
it here instead:

> When debugging an instance, mounting the volume on another instance is the best way to go.
> This is a problem when the instance used for debugging and the instance to debug use the same AMI.
> The system will complain that the UUID of the root volume and the one of the buggy instance is the same. This is an unnecessary problem people have to fix by googling how to override that check.
> By changing the UUID on first boot, this problem can be avoided.

What do you guys think, is this a sensible thing to do?

Anders