js .collapse() invocations don't toggle the .collapsed class for any of the collapse control elements

Created by: er1c

Took me a while to track down a repro case, but I finally managed to pin it down.

Repro example: http://jsbin.com/jatatucojuru/1/edit

The docs say

If you'd like it to default open, add the additional class in.

And then to "Via JavaScript":

 $('.collapse').collapse()

If I do this (add "in" to the accordions's class, and then invoke $('.collapse').collapse() on load), the accordion elements lack the .collapsed class on the .panel-heading as you can see below:

If you manually just trigger the same accordions by clicking on them a few times, everything starts working fine again: