Clean up linkpath between entries (#2343)

Clean up linkpath between entries (#2343)

PR #2127 failed to clean up the linkpath storage between entries. As a
result, after the first hard/symlink entry in a pax format archive, all
subsequent entries would get the same link information.

I'm really unsure how this bug failed to trip CI. I'll do some digging
in the test suite before I merge this.

Resolves #2331 , #2337

P.S. Thanks to Brad King for noting that the linkpath wasn't being
managed correctly, which was a big hint for me.