Issue #473: Update selectMenu method to set a default value.

On all pages with selectMenu (combobox) the user had to choose an
option to effectively store its value in the form.

This patch updates the function to use the first option as default
value. With this patch, user can skip the combo selection if want
use the first option.

Signed-off-by: Paulo Vital <pvital@linux.vnet.ibm.com>