CheckDriveSize reports perfdata in percent when threshold specified in percent

[Jeff Goldschrafe <goldschr@…>]

CheckDriveSize currently reports performance data to Nagios in percent when the threshold is specified in percent, e.g. MinWarnFree?=4%. I think that the check should always return the performance data in bytes (or kilobytes, megabytes, gigabytes, etc.) as the integer percentage makes it useless for trending, e.g. determining discrete storage growth over a period of weeks or months.