Disk CPU Load test needs improvement

[Jeff Lane ]

On a recent failed test, this is the output:

Testing CPU load when reading 4096 MiB from /dev/sda
Maximum acceptable CPU load is 30

This needs to be more informative, helpful in failures (and should remain as quiet as possible on success, though initially, we probably want more verbose output on success as well just to get a feel for what we're actually seeing).

I'd suggest the following:

1: Improve output on Failures, period.
2: Add a verbosity flag to increase verbose output on success as well (or perhaps something more like debug output).

Of course, those are just starting suggestions, the final changes could be different, so long as they meet the goal of enhancing output so debugging failures is easier.