How to configure Munin to not send alerts for sleeping disks

If you're using hard disks that are optimised for power efficiency or are mobile devices (which are set to be power efficient by default) you may get erroneous unnecessary warning email from Munin complaining about being unable to retrieve temperature and SMART data for those disks when they're sleeping. This can happen if the installed Munin is incorrectly handling the (2) exit code returned by…