The compression mode after it's set via config-changed might take a
while to fully propagate to the whole cluster, hence the hook may be
done before the cluster is fully configured with the new compression
mode. This is more noticeable in the gate when there are many jobs
running in parallel.
This patch modes the check to its own method wrapped with a
tenacity.retry decorator to make the test more robust.
Closes#946
618fb7b6e9