prod-202104-27: Fix stall problem in pipeliner runner in environments with nice>0

This is fixing a stall problem in the pipeline runner, which was
observed on systems (GRID), where the runner was launched with an
increased nice value (>0).

In this scenario, allocated resources per task were not correctly
"un-accounted' and so the runner stalled at some moment since it couldn't
find free resources.

This commit is also adding some debugging mechanism with webhooks.
Later integration into the standard logging system would be nice.