Prefer to report the Debian package version when available.

The intent of the version-reporting code appears to be to report the package
version if available, falling back to the hardcoded version otherwise.

However, the code doesn't match the comment - it actually picks the *last*
available value for a key, stomping on earlier values.

Update the comment and the value ordering so that the package version is
set last and takes priority over the hardcoded version.