Make NetworkInterfaceASIO stress test less stressful

The NIA stress test has become increasingly flaky on our windows testing machines, which cannot handle the load created by the test. In the past, we've been able to dial up the parameters to network_interface_asio_integration_test to reproduce rare bugs in the networking code, so we would like to not remove this test completely. Let's dial down the stressfulness of this test on average runs so we can maintain it as a tool to reproduce emergency situations.