In #2635 we broke the Manage PR CI job but for some reason CI didn't run
on that PR so we merged the breakage.
Fix the script by setting default variables when they are not set. Done
with ChatGPT.
Add `euo pipefail` to all non-trial shell scripts, note if `x` is
already set we maintain it.
Note we have a pipe in `run_task.sh` that relies on grep not finding
anything i.e., failing, so we cannot use pipefail there. Disable it and
re-enable it after the pipe.
Tobin C. Harding
Martin Habovstiak