Code review comment for lp:~nuclearbob/utah/cobbler-cleanup

I think that in the _cleanuptmpdir method is confusing to use a variable
that is named `filename` when it could be both a filename or a dirname.
I'd prefer something like `name`, but since that's already used in the
loop for the relative name, maybe `absolute_name` is a good choice
(also `path`, `absolute_path` might be good alternatives).