Ticket 562 - Crash when deleting suffix
    
    Bug Description:  If you delete a suffix you can crash the server if
                      you do not have a backend "userRoot".
    
    Fix Description:  Not sure why the nsme userroot needs to be present, maybe
                      it impacts the callback linked list order, not sure.  So
                      in dse_call_callback we grab the next callback before
                      calling the callback function.  It's possible that one of
                      these callbacks will unregister other callbacks - potentially
                      the "next" callback that we already put aside.  So it
                      gets freed, and then its read on the next pass which crashes
                      the server.
    
                      The fix is just to not "pre grab" the next callback, and
                      wait until after the callback function returns to move on
                      to the next callback.
    
                      Note:  this only appears to happen on 32-bit platforms.
    
    https://fedorahosted.org/389/ticket/562
    
    Reviewed by: Ludwig & nkinder(Thanks!)