'Verify the cache volume of a bootable volume.
If the cache no longer has clone, it will be deleted.'

@utils.synchronized('zfssanfs', external=True)
def _check_origin(self, origin):

    try:
        cachevol_props = self.zfssa.get_volume(origin)
    except exception.VolumeNotFound:
        LOG.debug('Origin    %s    does    not    exist', origin)
        return
    numclones = cachevol_props['numclones']
    LOG.debug('Number    of    clones:    %d', numclones)
    if (numclones <= 1):
        self.zfssa.delete_file(origin)
    else:
        cachevol_props = {'numclones': six.text_type((numclones - 1))}
        self.zfssa.set_file_props(origin, cachevol_props)
