'Return the concrete action object, not just a generic OozieAction'

def get_root_action(self):

    root = self.root_action
    if (root is None):
        return None
    if (root.action_type == OozieMapreduceAction.ACTION_TYPE):
        return root.ooziemapreduceaction
    elif (root.action_type == OozieStreamingAction.ACTION_TYPE):
        return root.ooziestreamingaction
    elif (root.action_type == OozieJavaAction.ACTION_TYPE):
        return root.ooziejavaaction
    LOG.error(("Oozie    action    type    '%s'    is    not    valid    (jobsub_oozieaction.id    %s)" % (root.action_type, root.id)))
    return None
