HPCC-12515 no_datasetfromrow should always traverse input

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
It almost certainly isn't, but it is good enough.  It was partly got by trial and error of looking at the regression suite differences, and working out what else should go in here.
There are lots of other outstanding jiras (e.g., conditional execution) which really need tackling before this can be in any way definitive.