branchcache: cleanup the final key generation after update A lot of duplicated work seemed to be done, as we already update the tiprev and tipnode when needed right before. So we simplify that part to focus on the filtered hash. See inline comment for details.

  $ LANG=nonexistent LC_ALL=nonexistent LANGUAGE=nonexistent hg version -q
  Mercurial Distributed SCM (version *) (glob)