Change name we use for virtio serial consoles
    
    There is nothing inherently 'root'-y about these so it makes no
    sense to prefix their names with 'root-'. And why change from
    'console' to 'terminal' compared to the naming used in the
    actual qemu command and the log files? It's just confusing.
    Let's be consistent (except for using - instead of _ here...
    but - is easier to type!)
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>