Code review comment for lp:~colin-king/ecryptfs/misc-fixes

Thanks, Colin! The only thing that caught my eye was the off_t to size_t changes. Since we're dealing with a file size, we should be using off_t rather than ssize_t (ssize_t wraps at 2GB on 32 bit machines). But, I see where other portions of that test use ssize_t so this change doesn't make us any worse off than what we already are at this point.