fix(core): Use ogroups instead of posix when mixed-group is installed

When mixed-groups is installed, the userGroupSelect dialog should allow
 to select object groups as they can be posix groups as well

issue #5694

include/select/userGroupSelect/class_userGroupSelect.inc

@@ -22,6 +22,14 @@ class userGroupSelect extends userSelect
 {
   protected $objectTypes = array('user', 'group');
   protected $autoFilterAttributes = array('dn', 'cn', 'uid', 'description');
+
+  function __construct()
+  {
+    if (class_available('mixedGroup')) {
+      $this->objectTypes = array('user', 'ogroup');
+    }
+    parent::__construct();
+  }
 }
 
 class userGroupRoleSelect extends userGroupSelect