HPCC-12239 Only track expressions as conditional within a workflow item

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #6439 from ghalliday/issue12239

HPCC-12239 Only track expressions as conditional within a workflow item

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>