[TIMOB-11910] iOS: WebView - rendering issue after remote URL is opened

Description: While testing Web view, I noticed rendering problem when page content is changing. There is a partial black screen appearance before the next view displayed. It happens on iPhone5 and iPad mini with iOS 6.0. iPad3,4 do not have this issue. This issue disappears after pinch/zoom of the view. *not a regression*, occurs in 2.1.4 looks like devices specific. Test stept: 1. Run the code below:

var win = Ti.UI.createWindow({  
    backgroundColor:'#fff'
});
win.open();

var button1 = Titanium.UI.createButton({
		    top: 330,
		    title: 'Open Remote URL With Spinner',
		    style: Titanium.UI.iPhone.SystemButtonStyle.BORDERED
		});
		 
		button1.addEventListener('click', function(e) {
		    var webview = Titanium.UI.createWebView({
		        top: 0,
		        width: 320,
		        height: 320,
		        url: 'http://www.appcelerator.com', 
		    });
		     
		    win.add(webview);
		});
		 
		win.add(button1);

2. Watch a view behavior. Actual result: Black screen appearance before view change. Expected: Proper render of views.