Sharing fix permissions

make sure that we always return the correct permissions.

How to test:

- Create a folder "folder"
- Upload a file to "folder", e.g. "test.txt"
- share the folder with user2, remove all permissions
- login as user2
- the folder should have permissions to delete (unshare) and rename
- navigate to the folder
- file in the folder should only have read permissions (without this patch the file will also have delete and rename permissions)

@icewind1991 please have a look, since this also touches the oc filesystem.

This is wrong, `$internalPath` is *not* for the sub storage, `''` is correct here since it's always the root of the substore we want to show