Major Description
RMD command should not delete the current working directory or the any parent of current working directory.
case 1: Let us say, the current working directory is "/wd" then "RMD ." or RMD "/wd" should result in a 5XX reply.
case 2: Let us say the working directory is "/wd/subdir", then RMD /wd or "RMD .." should also be restricted and a 5xx reply should be sent.