[TIMOB-4647] Android: TableView backgroundColor disables the system row selector

If a TableViewRow has a custom backgroundColor set, and no backgroundSelectedColor or backgroundSelectedImage, then the system's row selector doesn't seem to get used. Here's a simple example:

var win = Ti.UI.createWindow({
    top: 0, left: 0, bottom: 0, right: 0,
    backgroundColor: "white"
});

var table = Ti.UI.createTableView({
    data: [ { title: "Custom background", backgroundColor: "yellow", color: "black" } ]
});
win.add(table);
win.open();

When you touch the yellow row, the system's default selector should highlight it, but currently nothing is happening.