If the delete call fails, the file will be marked as "deleted" in the database even though it may not actually be deleted.
Once the delete grace time expires, Duplicati will refuse to run backups as a "new" file is found in the destination folder.
This PR changes the logic to track if the file was actually deleted, and will not mark the file deleted until the delete call reports success.
This fixes#6539
Kenneth Skovhede