http-walker: free fake packed_git list

The dumb-http walker code creates a "fake" packed_git list representing packs we've downloaded from the remote (I call it "fake" because generally that struct is only used and managed by the local repository struct). But during our cleanup phase we don't touch those at all, causing a leak. There's no support here from the rest of the object-database API, as these structs are not meant to be freed, except when closing the object store completely. But we can see that raw_object_store_clear() just calls free() on them, and that's enough here to fix the leak. I also added a call to close_pack() before each. In the regular code this happens via close_object_store(), which we do as part of raw_object_store_clear(). This is necessary to prevent leaking mmap'd data (like the pack idx) or descriptors. The leak-checker won't catch either of these itself, but I did confirm with some hacky warning() calls and running t5550 that it's easy to leak at least index data. This is all much more intimate with the packed_git struct than I'd like, but I think fixing it would be a pretty big refactor. And it's just not worth it for dumb-http code which is rarely used these days. If we can silence the leak-checker without creating too much hassle, we should just do that. This lets us mark t5550 as leak-free. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>