Double border problem on .input-group-btn

Created by: Petercopter

http://getbootstrap.com/components/#input-groups

In the example and in practice, .input-group-addon is working correctly, but .input-group-btn is not. Both the input and the buttons retain their borders, so you end up with a 2px instead of 1px border between the buttons and the input.

It was working correctly in 3RC1.