**Do you want to request a *feature* or report a *bug*?**

bug

**What is the current behavior?**

componentWillUnmount for inner instances is never called.

Here are 2 (jest) tests, the first works, not the second.

```js
import React from "react";
import renderer from "react-test-renderer";

test("top level componentWillUnmount works", () => {
  let count = 0;
  class A extends React.Component {
    componentWillUnmount() {
      count ++;
    }
    render() {
      return <div />;
    }
  }
  const inst = renderer.create(<A />);
  inst.unmount();
  expect(count).toEqual(1);
});

test("inner componentWillUnmount works", () => {
  let count = 0;
  class A extends React.Component {
    componentWillUnmount() {
      count ++;
    }
    render() {
      return <div />;
    }
  }
  const inst = renderer.create(
    <div>
      <A />
    </div>
  );
  inst.unmount();
  expect(count).toEqual(1);
});
```

**What is the expected behavior?**

The two test above should pass. All component that are unmounted should have the proper lifecycle, whatever the nesting is.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**

React 15.4.0
/**
 * Copyright 2013-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule ReactTestRenderer
 * @preventMunge
 * @flow
 */
'use strict';
var ReactComponentEnvironment = require('ReactComponentEnvironment');
var ReactDefaultBatchingStrategy = require('ReactDefaultBatchingStrategy');
var ReactEmptyComponent = require('ReactEmptyComponent');
var ReactMultiChild = require('ReactMultiChild');
var ReactHostComponent = require('ReactHostComponent');
var ReactTestMount = require('ReactTestMount');
var ReactTestReconcileTransaction = require('ReactTestReconcileTransaction');
var ReactUpdates = require('ReactUpdates');
var ReactTestTextComponent = require('ReactTestTextComponent');
var ReactTestEmptyComponent = require('ReactTestEmptyComponent');
var invariant = require('invariant');
import type { ReactElement } from 'ReactElementType';
import type { ReactInstance } from 'ReactInstanceType';
type ReactTestRendererJSON = {
  type: string,