[#33805] Only try to find a search page if the request Itemid is not a search page.

Also, find search pages by component id, not link string

Fixes this tracker item: http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=33805
FWIW, I think the only libraries folder we don't have autoloaded classes in is the `joomla` folder.  Since `cms` and `legacy` were started after we had the autoloader, there was more concern with getting it right when adding classes to those locations.