'If the known era matches, ``UpdateNodeStateEra`` does nothing.'

def test_same_era(self):

    state = self.UPDATE_ERA_1.update_cluster_state(self.INITIAL_CLUSTER)
    state = self.NODE_STATE.update_cluster_state(state)
    updated_state = self.UPDATE_ERA_1.update_cluster_state(state)
    self.assertEqual(state, updated_state)
