backport of https://github.com/owncloud/core/pull/5513
make getUidAndFilename() private
make sure that also the storage etag gets changed
Merge branch 'master' into fix_file_cache_updater_master
Merge pull request #5603 from owncloud/fix_file_cache_updater_master

Fix file cache updater (backport to master of #5513)