Mount the named image via qemu-nbd and return the mounted roots

    CLI Example:

    .. code-block:: bash

        salt '*' qemu_nbd.init /srv/image.qcow2

def init(image, root=None):
    '''
    Mount the named image via qemu-nbd and return the mounted roots

    CLI Example:

    .. code-block:: bash

        salt '*' qemu_nbd.init /srv/image.qcow2
    '''
    nbd = connect(image)
    if not nbd:
        return ''
    return mount(nbd, root)