Test With More Threads

[insertinterestingnamehere]

Even though the CI workers are small, we should be testing with more threads for the "basics" and "features" sections of the test suite. Given that some of the schedulers are hierarchical it should probably be two shepherds and two workers per shepherd by default.

The stress tests actually use many more threads by default and we may want to consider decreasing the default value there.

For reference when fixing: these things are set by command line arguments to the tests as well as some environment variables and are managed in the Makefile.am in each test subdirectory.