Fixed const correctness.. I know it's a hack but fixing it correctly would...

Fixed const correctness.. I know it's a hack but fixing it correctly would take a lot of time for no gain since this is already being refactored

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@1009 41f8697f-d340-4b68-9986-7bafba869bb8