'This adds a image to be cache to the queue.
If the image already exists in the queue or has already been
cached, we return False, True otherwise
:param image_id: Image ID'

def queue_image(self, image_id):

    if self.is_cached(image_id):
        LOG.info(_LI("Not    queueing    image    '%s'.    Already    cached."), image_id)
        return False
    if self.is_being_cached(image_id):
        LOG.info(_LI("Not    queueing    image    '%s'.    Already    being    written    to    cache"), image_id)
        return False
    if self.is_queued(image_id):
        LOG.info(_LI("Not    queueing    image    '%s'.    Already    queued."), image_id)
        return False
    path = self.get_image_filepath(image_id, 'queue')
    with open(path, 'w'):
        pass
    return True
