[LIBCLOUD-639] Python 3 Error: "Invalid argument %r for b()" when using upload_object_via_stream

https://issues.apache.org/jira/browse/LIBCLOUD-639
Looked at it again in a debugger and it appears this only affects storage drivers with `supports_chunked_encoding = True`, i.e. the Atmos and Rackspace drivers at this time.
https://github.com/apache/libcloud/blob/trunk/libcloud/storage/base.py#L634-636

Otherwise it uses the else branch directly below and consumes the entire iterator as already documented:
https://github.com/apache/libcloud/blob/trunk/libcloud/storage/base.py#L400-408