always cleanup patchfiles at the end of rred call

always cleanup patchfiles at the end of rred call

With APT::Get::List-Cleanup disabled the ed-style patch files are
lingering in the lists/ directory otherwise. That was kinda okay in the
old none-client-merge as the filename was always the same so it was
constantly overridden, but now with different names for client-merge
quiet a few could pill up on the system and are used by the next call
as it picks them up based on the filename.