[TIMOB-2183] iOS: zindex not working correctly

Running on master as of 10/24, zIndex seems broken.

Here's the test case. Pink should be on top.

var window = Ti.UI.createWindow();
var view1 = Ti.UI.createView({
    backgroundColor:'pink',
    zIndex:20,
    width:200,
    height:30,
    top:10,
    left:10
});

var view2 = Ti.UI.createView({
    backgroundColor:'blue',
    zIndex:11,
    width:200,
    height:30,
    top:15,
    left:15
});

var view3 = Ti.UI.createView({
    backgroundColor:'red',
    zIndex:12,
    width:200,
    height:30,
    top:20,
    left:20
});

window.add(view1);
window.add(view2);
window.add(view3);
window.open();