virsh domxml-from-native to treat SCSI as the bus type for pseries by default
    
    The bus type IDE being enum Zero, the bus type on pseries system appears as IDE for all the -hda/-cdrom and for disk drives with if="none" type. Pseries platform needs this to appear as SCSI instead of IDE. The ide being not supported, the explicit requests for ide devices will return an error.
    
    Signed-off-by: Shivaprasad G Bhat <sbhat@linux.vnet.ibm.com>