Evergreen task disk statistics improvement

We are using iostat or vmstat (Linux/Unix) & typeperf (Windows) for disk statistics (SERVER-24212). We should improve this output as follows:

• Have iostat installed on all Linux/Unix hosts that support it
• Use additional parameters for iostat (-m -x)
• Add timestamp for each time period it reports (See this article for what to do if -t option is not available)