[Libguestfs] [PATCH] Add ata_piix to kernel module whitelist (RHBZ#533886).

Charles Duffy discovered this module is missing and required when we're using libguestfs on RHEL 6 Alpha. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://et.redhat.com/~rjones/virt-df/