jquery.makeCollapsible.test: Use fake timers to advance animations

This is essentially a headless test. No point in slowing down
the QUnit run with dozens of gaps where we wait for 400ms for
some jQuery fade animation to run to completion.

On Chrome 33, this reduced run time for jquery.makeCollapsible
tests from 7631ms to 179ms.

Change-Id: I3723329fc0139da631bd047cb720bab1c2f754d9
Merge "jquery.makeCollapsible.test: Use fake timers to advance animations"