Enable debug trace in knightly pipeline with variable

Trying to debug issue with the latest failed pipeline: https://gitlab.rc.uab.edu/rc/packer-openstack-hpc-image/-/jobs/41191

added Sprint 24-3 label

assigned to @louistw

changed milestone to %WIP: OOD knightly improvement

mentioned in merge request !76 (closed)

changed the description

Turns out, Gitlab CI already has a predefined CI variable for this purpose, it's called: CI_DEBUG_TRACE

closed