Add fio_benchmark.py test for multiple scenarios
Add fio_benchmark.py test for multiple scenarios

Done in response to review comments.

lleszczu/PerfKitBenchmarker,AdamIsrael/PerfKitBenchmarker,GoogleCloudPlatform/PerfKitBenchmarker,kivio/PerfKitBenchmarker,GoogleCloudPlatform/PerfKitBenchmarker,mateusz-blaszkowski/PerfKitBenchmarker,syed/PerfKitBenchmarker,GoogleCloudPlatform/PerfKitBenchmarker,lleszczu/PerfKitBenchmarker,meteorfox/PerfKitBenchmarker,mateusz-blaszkowski/PerfKitBenchmarker,AdamIsrael/PerfKitBenchmarker,GoogleCloudPlatform/PerfKitBenchmarker,syed/PerfKitBenchmarker,meteorfox/PerfKitBenchmarker,kivio/PerfKitBenchmarker