qunit/testrunner: Log relevant node in unfinished animations and reset

qunit/testrunner: Log relevant node in unfinished animations and reset

Having unfinished animations affect other test can be a problem,
but when it does happen, having just a number isn't helpful in
trying to pinpoint the cause.

Logging a description of the element should make this relatively
straight forward.

Also reset the animations after the test so that the next test has a
clean start (instead of the current situation where every subsequent
test, until the animation finishes, also reports it as a failure).

Example:

 Unfinished animation #0 in fx queue on <div class="mw-notification
  mw-notification-tag-legacy" style="opacity: 0; "/>

Change-Id: I41058c4cba3383e3ad1456990ccf8dae4ca64951