object: fix leaking packfiles when closing object store

object: fix leaking packfiles when closing object store

When calling `raw_object_store_clear()`, we close and free several
resources associated with the object store. Part of that is to close and
free all the packfiles, which is handled by `close_object_store()`.

That function really only ends up closing the packfiles though, but it
doesn't free them. And in fact it can't, as that function is being
called via `run_command()` when `close_object_store = 1`, which is done
e.g. when we execute git-maintenance(1). At that point, other structures
may still have references on those packfiles, and thus we cannot free
them here. So while it is in fact intentional that we really only close
them, the result is a memory leak because `raw_object_store_clear()`
does not free them, either.

Fix the leak by freeing the packfiles in `raw_object_store_clear()`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>