[TIMOB-11571] Android: opening a modal window from another modal shows a flickering transition

Description problem

Opening a modal window from another modal shows a flickering transition; the problem is not happening all the times, but almost (I'd say more than 90%).

Steps to reproduce

- Create an app with this code:

var num = 1;
function createWin() {
    var win = Ti.UI.createWindow({
        backgroundColor: 'black',
        modal: true
    });
    
    var image = Ti.UI.createImageView({
        image: '/images/' + (num++ % 3 + 1) + '.jpg',
        top: 10,
        left: 10,
        width: 300,
        height: 200
    });
    
    win.add(image);
    
    var button = Ti.UI.createButton({
        title: "Next",
        top: 300
    });
    
    button.addEventListener('click', createWin);
    
    win.add(button);
    
    win.open();
}

createWin();

- Put 3 different images in the Resources/images directory (I set 300x200) - Run the app and click Next: most of the times the next window is shown for a fraction of second, then the current window is shown again before the second is fully opened (e.g. you see a flickering effect).

Additional notes

The problem does not happen with lightweight windows, but in that case the back button wouldn't work; if modal is set to false, the problem does not happen as well, but the animation of the opening window is not so nice as well.