Initialise client objects for talking to OpenStack API.

        This is in a separate function so to be called by ``__init__`` and
        ``__setstate__``.

def __init_os_api(self):
        """
        Initialise client objects for talking to OpenStack API.

        This is in a separate function so to be called by ``__init__`` and
        ``__setstate__``.
        """
        loader = loading.get_plugin_loader('password')
        auth = loader.load_from_options(auth_url=self._os_auth_url,
                                        username=self._os_username,
                                        password=self._os_password,
                                        project_name=self._os_tenant_name)
        sess = session.Session(auth=auth)
        self.nova_client = nova_client.Client(self.nova_api_version, session=sess)
        self.neutron_client = neutron_client.Client(session=sess)
        self.glance_client = glance_client.Client('2', session=sess)
        self.cinder_client = cinder_client.Client('2', session=sess)