[TIMOB-15777] iOS: Window focus event not called for the first time when window added on tab group

app.js
var tabGroup = Titanium.UI.createTabGroup();
 
var win1 = Titanium.UI.createWindow({  
    title:'Tab 1',
    backgroundColor:'#fff',
    url:'win1.js'
});
 
var tab1 = Titanium.UI.createTab({  
    icon:'KS_nav_ui.png',
    title:'Win 1',
    window:win1
});
 
var win2 = Titanium.UI.createWindow({  
    title:'Tab 2',
    backgroundColor:'#fff',
    url:'win2.js'
});
 
var tab2 = Titanium.UI.createTab({  
    icon:'KS_nav_ui.png',
    title:'Win 2',
    window:win2
});


 
tabGroup.addTab(tab1);
tabGroup.addTab(tab2);
 
tabGroup.open();


win1.js

var win1 = Ti.UI.currentWindow;
win1.addEventListener('focus',function(e){
    alert('test win1');
});

win2.js

var win2 = Ti.UI.currentWindow;
win2.addEventListener('focus',function(e){
    alert('test win2');
});