[Natty] Revert Ubuntu specific patch to name virtual Xen block devices sd

[John Johansen]

On 01/05/2011 02:03 AM, Stefan Bader wrote:
> I did a quick test of the patch reverted and had no problems in booting the
> instance with the xvd* names.
> 
> -Stefan

Acked-by: John Johansen <john.johansen at canonical.com>