Ticket 47396 - crash on modrdn of tombstone
    
    Bug Description:  a client modrdn operation on a tombstone entry can crash the server
    
    Fix Description:   client modrdns and modifies on tombstone entries should not be
    	accepted. Tombstones aer internally kept for eventual conflict resolution, normal
    	clients should not touch them.
    	an exception would be to force purging of tombstones or a kind of "undo" for
    	a delete, which could resurrect a tombstone, but this is not in the scope of this ticket
    
    https://fedorahosted.org/389/ticket/47396
    
    Reviewed by: Rich, thanks