revert: no backup for `dsadded` set
There is only one case where a backup is required in the `dsadded` set, and the
current backup mechanism fails to handle it. So we stop trying to do backups at
all for now. This will help us to simplify the backup code and finally fix
this backup issue.
http://example.com/no/anchor, branches: (None, [])
http://example.com/an/anchor, branches: ('foo', [])
http://example.com/no/anchor/branches, branches: (None, ['foo'])
http://example.com/an/anchor/branches, branches: ('bar', ['foo'])
http://example.com/an/anchor/branches-None, branches: ('foo', [])
http://example.com/, branches: (None, [])
http://example.com/, branches: (None, [])
http://example.com/, branches: ('foo', [])