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**Do you want to request a *feature* or report a *bug*?**
bug, I believe, unless I misunderstand how it works
**What is the current behavior?**
Given a `Suspense` inside `Suspense` case like
```
<Suspense fallback="Fallback 1">
  <LazyText1 text="First text" />
  <Suspense fallback="Fallback 2">
    <LazyText2 text="Second text!" />
  </Suspense>
</Suspense>
```

Promises in `LazyTexts` start resolving at the same time, but if `LazyText2` is resolved first it never renders, `Fallback 2` stays.

Result:
```
First text

Fallback 2
```

Please see https://codesandbox.io/s/234o4zry7n

**What is the expected behavior?**

Every `LazyText` displayed in the end
```
First text

Second text!
```

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
react, react-dom 16.6.0

ReactNoop.expire(4000);
    await advanceTimers(4000);
    expect(ReactNoop.flush()).toEqual([]);
    expect(ReactNoop.getChildren()).toEqual([
      span('Loading A...'),
      span('Loading B...'),
    ]);
    
    
    
    ReactNoop.expire(1000);
    await advanceTimers(1000);
    expect(ReactNoop.flush()).toEqual(['Promise resolved [A]', 'A']);
    expect(ReactNoop.getChildren()).toEqual([span('A'), span('Loading B...')]);
    
    
    ReactNoop.expire(1000);
    await advanceTimers(1000);
    expect(ReactNoop.flush()).toEqual(['Promise resolved [B]', 'B']);
    expect(ReactNoop.getChildren()).toEqual([span('A'), span('B')]);
  });
  it('continues rendering siblings after suspending', async () => {
    ReactNoop.render(
      <Suspense fallback={<Text text="Loading..." />}>
        <Text text="A" />
        <AsyncText text="B" />
        <Text text="C" />
        <Text text="D" />
      </Suspense>,