Ticket 47712 - betxn: retro changelog broken after cancelled transaction
    
    Bug Description:  If a transaction is aborted (eg failing automember) and
    			the retrocl is either broken (first txn after enabling rcl)
    			or there are gaps in the changenumbers
    			The reason that there are gaps in changenumbers is that
    			if the txn is undone the entry is removed from the
    			RCL database, but the last changnumer was incremented already
    			The reason that the RCL seems to be broken is that
    			the entry is removed from the database, but is still in
    			the entry cache. For the first change the changenumber is
    			always recreated and it detects the entry in the entrycache
    			and returns "already exists". If the gaps would be avoided
    			this would also happen for later failures.
    Fix Description:   If the RCL postop function is called with an error set in the
    			pblock, set a flag that next time a chnagenumber will be
    			assigned it is recreated from the database.
    		   It is not possible to remove the CL entry from the entry cache
    			from the RCL plugin, cache functions are not available.
    			The only solution is to avoid keeing RCL entries in the
    			entry cache after their initial creation. Extend the
    			operation flags to trigger a removal from cache in
    			ldbm_back_add()
    
    https://fedorahosted.org/389/ticket/47712
    
    Reviewed by: richm, thanks