Ticket #321 - krbExtraData is being null modified and replicated on each ssh login
    
    Bug Description:  When using fractional repl, if you update a attribute that is excluded,
                      a modify op is still sent to the replicas.  The update is basically empty,
                      except we are still updating these attributes for no reason:
    
                         modifiersname
                         modifyTimestamp
                         etc
    
    Fix Description:  Added a new attribute to the replication agmt:  nsds5ReplicaStripAttrs
    
                      Add the attributes that you don't want replicated if the mods are "empty".
                      Separate each attribute by a space:
    
                         nsds5ReplicaStripAttrs: modifiersname modifytimestamp
    
    Side Note:  Did a little optimization in repl5_strip_fractional_mods() as well.
    
    https://fedorahosted.org/389/ticket/321
    
    Reviewed by: