libarchive: tar: fix memory leaks when reading symlinks or parsing pax headers

Backport [libarchive PR 2338] to fix [libarchive issue 2336].

[libarchive PR 2338]: https://github.com/libarchive/libarchive/pull/2338
[libarchive issue 2336]: https://github.com/libarchive/libarchive/issues/2336