Automatic merge from submit-queue

Allow for overriding throughput in load test

We seem to be already supporting higher throughput that what the default is.

I'm going to increase the throughput in our tests:
- speed up scalability tests
- ensure that what I'm seeing locally is really the repeatable case

This PR is a short preparation for those experiments.

[Ideally, I would like to have kubemark-500 to be finishing within 30 minutes. And I think this should be doable pretty soon.]

@gmarek