[refpolicy] Take virtio disks into account

[Mika Pflüger]

Hi,

When using selinux in a virtualized system with virtio disks, the virtio
devices (/dev/vd*) are not labelled correctly. This can be fixed by this one-
liner, treating virtio disks just like any other disk (sata, ide, etc).

Without this patch, the booting grinds to a halt when selinux denies mounting
the root fs (which has to reside on a virtio disk, of course).

Cheers,

Mika Pflüger