HPCC-10462 - Fix problem retrying add/remove ops in transactions

If a transaction fails (due to other locks), it will unlock the
files it has gained preparing the transaction thus far, pause
and try again.
HPCC-9218 tracked which pending operations were to occur, so
that multiple transactional ops would correctly detect if a sub
file had already been removed or added. This introduced this
regression, because when a transaction retries, these tracked
files need to cleared.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Merge pull request #5177 from jakesmith/hpcc-10462

HPCC-10462 - Fix problem retrying add/remove ops in transactions

Reviewed-By: Gavin Halliday <gavin.halliday@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>