Ticket 47853 - client hangs in add if memberof fails
    
    Bug Description:  If memberof plugin is enabled and the client adds an
                      entry with a membership attr it hangs if the memberof_postop_add
                      rejects the operation.
    
    Fix Description:  The problem is due to an unexpected error code being set
                      in the pblock (-1).  Setting the proper LDAP error code
                      resolves the hang.
    
    https://fedorahosted.org/389/ticket/47853
    
    Reviewed by: lkrispenz(Thanks!)