To support calling find_non_local_tags() more than once in a single
git-fetch process we need the existing_refs to be stack-allocated
so it resets on the second call. We also should free the path
lists to avoid unnecessary memory leaking.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>