am use_token: if True, uses the token in the response received from the auth request to set the "token"
            attribute on the the :py:meth:`hvac.adapters.Adapter` instance under the _adapter Client attribute.
        :type use_token: bool
        :param mount_point: The "path" the method/backend was mounted on.
        :type mount_point: str | unicode
        :return: The JSON response of the login request.
        :rtype: dict
        