**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
var {children, ...props} = this._currentElement.props;
    var childrenJSON = [];
    for (var key in this._renderedChildren) {
      var inst = this._renderedChildren[key];
      inst = getRenderedHostOrTextFromComponent(inst);
      var json = inst.toJSON();
      if (json !== undefined) {
        childrenJSON.push(json);
      }
    }
    var object: ReactTestRendererJSON = {
      type: this._currentElement.type,
      props: props,
      children: childrenJSON.length ? childrenJSON : null,
    };
    Object.defineProperty(object, '$$typeof', {
      value: Symbol.for('react.test.json'),
    });
    return object;
  }
  getHostNode(): void {}