ensure compression cleanup even without lists-cleanup

ensure compression cleanup even without lists-cleanup

If we store files compressed in lists/ and the file switched compression
formats we happened to retain the "old" format, but by default the
cleanup process catched this oversight and removed the file.
[The initial situation described doesn't arise as we store no files by
default compressed and even with apt-file configuring Contents files, we
don't really have that problem as there is just .gz files for those.]

We solve this by just removing any uncompressed as well as compressed
(we support) file just before we move the 'new' version of the file in.