Eng 6607 - Add support for truncate table to DR2

The introduction of "fallible" like this seems to say "If DR should ever find itself operating within an undo context, it should quietly ignore it for this particular operation." Seems risky -- is this a real scenario, where all other DR operations work correctly or is it a sign of something horribly wrong -- would it make sense to assert that we are NOT actually in this strange edge case of having an undo quantum in a DR replay context.