* fixes #17757

When returning a 500 statuscode external applications may interpret this as an error instead of handling this more gracefully. This will now make return a 401 thus.

Fixes https://github.com/owncloud/core/issues/17742

Memcache factory expects a class name, not an instantiated object

Warning is now printed to logs, but occ and cron will still work.

If PROPFIND fails with 404 or 405 on the remote share root, it means the
storage is not available. Throw StorageNotAvailable is such case.

Remove information about whether a file is an incoming share or mount
point when requested over public webdav.