Bug 1710735: user list sorting by column field

sortby field was being forced to be 'lastname'
sortdir to be 'asc'
in the search url for each header.

behatnotneeded

Change-Id: I6c78eab1c8570bb0408c08a34d2f62890313085c
(cherry picked from commit 3e31e8de)

htdocs/lib/searchlib.php

@@ -397,7 +397,7 @@ function get_admin_user_search_results($search, $offset, $limit) {
 function build_admin_user_search_results($search, $offset, $limit) {
     global $USER, $THEME;
 
-    $wantedparams = array('query', 'f', 'l', 'sortby', 'sortdir', 'loggedin', 'loggedindate', 'duplicateemail', 'institution', 'authname');
+    $wantedparams = array('query', 'f', 'l', 'loggedin', 'loggedindate', 'duplicateemail', 'institution', 'authname');
     $params = array();
     foreach ($search as $k => $v) {
         if (!in_array($k, $wantedparams)) {