Added check for "chzn-done" class name in order to let Chosen skip SELECT elements

In the previous version of Chosen, one could render a `select` element with class name `chzn-done` so that Chosen would skip it and not try to treat it with the Chosen UI.

This is no longer possible since version 3.2.3 and no alternative way to render regular select is provided.

Proposed is the addition of the check for the class `chzn-done` like it used to be.

[JoomlaCode [#33449]](http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=33449&start=0)