Minor changes to Python test harness to allow it to be used on Windows.  Closes #4366

We have some tests for the Raven framework that we want to run on Windows.  There are a couple of small issues that prevent it from running out of the box with the Windows Python distribution.
While this works, it's a complicated piece of code that could change. I think a better solution would be to wrap `getloadavg`, i.e. test if `getloadavg` is there and if it's not just set a local variable representing load average to zero so that it doesn't ever effect the loop condition.