Fixes #9920: Radio checked property is removed on second click with data-toggle="buttons"

The radio checked property is removed on second click with data-toggle="buttons" as stated in [issue #9920](https://github.com/twbs/bootstrap/issues/9920). Also in the change event the active class is still on the previous active label.

How it currently works: http://jsfiddle.net/mauvm/atuYM/ (see console)
The solution: http://jsfiddle.net/mauvm/f9dsS/