Bootstrap3 collapse consecutive transition fix and tidy

Found a bug that allowed consecutive transitions. If you click three times quickly, it would break this Bootstrap 3 version. This should be backported to the current collapse though it isn't causing any visible issues.

This is partially because there's a bug in `$transition` that wouldn't correctly call all the transition end listeners due to https://github.com/angular/angular.js/pull/5109 . Yes, it was two bugs in separate places that was making it difficult to solve this one.