AsyncServletOutputStreamWriterConcurrencyTest is too slow

[ejona86]

On my laptop, the single linCheck test takes over four minutes. I believe this is adding roughly that amount of time to the total build. This test class should either not be part of the normal test execution, or be configured in such a way to take considerably less time (max of 30s?).

I tried reducing OPERATIONS_PER_THREAD from 6 to 4, but it still took over 2 minutes.