Update to OpenAFS-1.8.6; add helper script for future updates

• (added new_upstream_release.sh to facilitate future updates)
• motivation for going from 1.8.4 to 1.8.6:
  • 1.8.5 was a "security" fix (minor, but official advisories.. http://openafs.org/frameset/dl/openafs/1.8.5/RELNOTES-1.8.5 )
  • 1.8.6 has bugfixes for things actually seen in the wild with 1.8.4 (and 1.8.5), supposedly on RHEL7 and RHEL8 - per https://lists.openafs.org/pipermail/openafs-info/2020-August/042957.html