Disable regulary failing test about changing nickname for jabber multichat.

test/net/java/sip/communicator/slick/protocol/jabber/TestOperationSetMultiUserChat2.java

@@ -688,8 +688,10 @@ public void testLeave()
      * In <tt>testNickName</tt>, user nicknames will be changed
      * and we will check if changes are well reflected on both user
      * sides.
+     *
+     * @todo must be tested, it regulary fails, so it was disabled.
      */
-    public void testNickName()
+    public void disable_testNickName()
         throws OperationFailedException,
                OperationNotSupportedException
     {