FENNEL:  when CHECKPOINT_DISCARD is used for forceTxns rollback,  don't truncate txn list
FENNEL:  when CHECKPOINT_DISCARD is used for forceTxns rollback, 
don't truncate txn list

[git-p4: depot-paths = "//open/lu/dev/": change = 5746]

LucidDB/luciddb,LucidDB/luciddb,LucidDB/luciddb,LucidDB/luciddb,LucidDB/luciddb,LucidDB/luciddb,LucidDB/luciddb,LucidDB/luciddb,LucidDB/luciddb