core: osinfo - adding VirtIO to disk hotplug for ppc

osinfo properties:
adding 'VirtIO' to ppc64.devices.disk.hotpluggableInterfaces

Change-Id: If87f5ec844bf4ae41e94c7702e52b059af0d59a2
Bug-Url: https://bugzilla.redhat.com/1155223
Signed-off-by: Daniel Erez <derez@redhat.com>