Bug 16903 - Multiple class attributes on catalog search tab

cat-search.inc contains an element with two class attributes, which is
invalid. This patch corrects it.

To test, apply the patch and view any page which uses the cat-search
include file to display the header search boxes. For instance, the
bibliographic detail page.

In the header, the "Search the catalog" box should be selected, and any
text you type in the box should be carried over when you switch to
different search tabs.

Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>