upgrade_MailScanner_conf helps automate the conversion of older MailScanner.conf config
files to the version of MailScanner you are installing. This takes care of adding any
new config items that need to be added, removing old deprecated items and updating the
comments, unless you specify --keep-comments to signal you want your old comments left.
--keep-comments - tells the script to not update the comments that have changed.
Using --keep-comments can cause you to not realize that there are new/more options
available to you for the item that your old comment was kept with.