fix(android): set default exitOnClose property to true

[m1ga]

fixes #13791

var win1 = Ti.UI.createWindow({
	backgroundColor: "green"
})
win1.addEventListener("click", function() {
	var win2 = Ti.UI.createWindow({
		backgroundColor: "red"
	})
	win2.open();
})
win1.open();

Steps to reproduce

• open the app (green window)
• click to open the second window (red)
• close the red window and close the green window right away
• you will see the root activity

more infos in the ticket