Zoho's WorkDrive listing API returns "401 R008 Unauthorized access"
(not a 404) when a folder id no longer resolves to a listable folder,
because it was deleted or never existed. A freshly refreshed token still
gets it, so it is not a token problem and retrying it is futile - and can
escalate to a 429 F7008 rate-limit penalty.
Handle it as a missing directory instead: shouldRetry no longer retries a
bare R008 401, listAll maps it to fs.ErrorDirNotFound, and
readMetaDataForPath flushes the stale parent from the dircache and reports
the object as not found so a later create re-resolves the parent. This lets
the VFS self-heal a stale cached directory id instead of hard-failing the
operation, and stops the VFS integration tests failing on a stale directory id.
Fixes#9578