Bug: 14471 Fix sorting by a name field.

This regression is related to Bug: 14463, as it was introduced with
the same change. In this case, since when we are sorting by a name field,
we use a "private" __lastname and __firstname attribute which
is not known by the driver's map, so it is ignored.

turba/lib/Object.php

@@ -194,9 +194,10 @@ public function setValue($attribute, $value)
             } catch (Turba_Exception $e) {}
         }
 
-        // If we don't know the attribute, and it's an email field, save it
-        // in case we need to populate an email field on save.
-        if (!isset($this->driver->map[$attribute]) && $attribute != '__tags') {
+        // If we don't know the attribute, it's not a private attribute,
+        // and it's an email field, save it in case we need to populate an email
+        // field on save.
+        if (!isset($this->driver->map[$attribute]) && strpos($attribute, '__') === false) {
             if (isset($attributes[$attribute]) &&
                 $attributes[$attribute]['type'] == 'email') {
                 $this->_emailFields[$attribute] = $value;