Ticket 48637 - DN cache is not always updated when ADD
     operation fails
    
    Bug Description:  When multiple backend txn plugins fail on an ADD operation
                      the dn hash of the entry cache is not updated correctly,
                      and the entry can be incorrectly returned by doing a search
                      using the entry DN as the base DN.
    
    Fix Description:  When we mark an entry from the cache as "deleted" remove the
                      entry from the entry cache's dn hash just in case cache_remove()
                      was not previously called.
    
    https://fedorahosted.org/389/ticket/48637
    
    Reviewed by: nhosoi(Thanks!)