Stable6 antivirus fix public upload and remove shipped tag 

- Removes shipped tag and correct version to fix complains while installing the app from appstore
- [stable6] Fixes broken anonymous upload  when app is enabled

Fixes https://github.com/owncloud/apps/issues/1807, https://github.com/owncloud/apps/issues/1836
backport of https://github.com/owncloud/apps/issues/1254 to stable6 as a bonus