Ticket 47808 - CI test: add test case for ticket 47808
    
    Bug Description: If be_txn plugin fails in ldbm_back_add, adding entry
                     is double freed.
    
    Test Description:
      It enables attribute uniqueness plugin with sn as a unique attribute
      Add an entry 1 with sn = ENTRY_NAME
      Add an entry 2 with sn = ENTRY_NAME
      If the second add does not crash the server and the following search
      found none, the bug is fixed.
    
    https://fedorahosted.org/389/ticket/47808