Camera inertia activates even though ScreenSpaceCameraController is disabled

I would expect the following code to make the globe stay put since `screenSpaceCameraController` is disabled between pressing on the mouse button and releasing it. However, while the globe doesn't drag normally, if you flick it the camera inertia causes the globe to move at the end.


``` javascript
var viewer = new Cesium.Viewer('cesiumContainer');
var scene = viewer.scene;
var canvas = scene.canvas;

canvas.addEventListener('pointerdown', function() {
scene.screenSpaceCameraController.enableInputs = false;
}, true);

canvas.addEventListener('pointerup', function() {
scene.screenSpaceCameraController.enableInputs = true;
}, true);
```

Start with the minimal Viewer reproduction and trace how scene.screenSpaceCameraController.enableInputs is handled during pointerdown, pointerup, and camera inertia. Confirm the expected behavior by checking that re-enabling inputs after a flick does not allow the globe to continue moving from pending inertia.

Written by the indexing model from the issue text.