Consider the new REST API instead of exec'ing sbatch for job submission.

[kkm000]

The previous approach was to start with 2, double and cap at 10: 2, 4, 8, 10, 10, ..., which was already traumatically slow.

The patch https://github.com/burrmill/burrmill/blob/master/lib/build/slurm/sbatch.19.patch reduces the poll time to 1s, which is a good value, given only a few instances are polling the cluster at a single time. However, this patch must be maintained, which is not the best option.

Slurm 20 introduced a REST API. As of v21, not all of command equivalents are covered. Consider using this API, in case it does not impose the same hard limit as the tool does.