HPCC-11920 Prevent SKIPiness leaking outside an ONFAIL

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #6241 from ghalliday/issue11920

HPCC-11920 Prevent SKIPiness leaking outside an ONFAIL

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>