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
    (cherry picked from commit d1d6245d6ab894cf56e2529cb5c5dc941f4843cd)
    (cherry picked from commit 7b35b724f8a874a200154d1e3626ed14cc5b8245)