fix: not drop first queue member if drop handler

[sorhawell]

resolves #413

If limiting cap and thereby active processes, while job queue was not empty, the first queue member would be dropped and never handled.

Solution: Just put first queue member back into queue, if no process is available due to downsizing of cap and active.

[sorhawell]

@eitsupi if I want to limit a test to only run in CI and not in interactive dev, because very exotic and takes a few seconds to run, should I do something like "skip if not en var CI='true' "?

[eitsupi]

I do not know how to gauge this. (Example in #413 no longer works.)
Since it seems to pass the test, is it safe to merge it?

[sorhawell]

It should also work with example in #413 I will check again and then merge. I added a test which should cause the same error , but it is as simple as possible to still cause the original error.