InvalidCredsError with upload_object_via_stream() on Aurora Objects

## Summary

When trying to upload a file to Aurora Objects through `upload_object_via_stream()`, I get an `InvalidCredsError`.

## Detailed Information

When I try the following code:

```python3
from libcloud.storage.types import Provider
from libcloud.storage.providers import get_driver

cls = get_driver(Provider.AURORAOBJECTS)
driver = cls('api-key', 'secret-key')

container = driver.get_container('container')

container.upload_object_via_stream(iter([b'test']), 'test.txt')
```

It results in the following error:

```
Traceback (most recent call last):
File "", line 1, in
File "/home/wout/project/.venv/lib/python3.9/site-packages/libcloud/storage/base.py", line 216, in upload_object_via_stream
return self.driver.upload_object_via_stream(
File "/home/wout/project/.venv/lib/python3.9/site-packages/libcloud/storage/drivers/s3.py", line 747, in upload_object_via_stream
return self._put_object_multipart(container=container,
File "/home/wout/project/.venv/lib/python3.9/site-packages/libcloud/storage/drivers/s3.py", line 988, in _put_object_multipart
upload_id = self._initiate_multipart(container, object_name,
File "/home/wout/project/.venv/lib/python3.9/site-packages/libcloud/storage/drivers/s3.py", line 572, in _initiate_multipart
response = self.connection.request(request_path, method='POST',
File "/home/wout/project/.venv/lib/python3.9/site-packages/libcloud/common/base.py", line 667, in request
response = responseCls(**kwargs)
File "/home/wout/project/.venv/lib/python3.9/site-packages/libcloud/common/base.py", line 167, in __init__
message=self.parse_error(),
File "/home/wout/project/.venv/lib/python3.9/site-packages/libcloud/storage/drivers/s3.py", line 138, in parse_error
raise InvalidCredsError(self.body)
libcloud.common.types.InvalidCredsError: 'SignatureDoesNotMatchtx00000000000004e0ebfe5-00620a68e9-1d4a885a-ams021d4a885a-ams02-eu'
```

However `upload_object()` is working fine as follows:

```python3
from libcloud.storage.types import Provider
from libcloud.storage.providers import get_driver

cls = get_driver(Provider.AURORAOBJECTS)
driver = cls('api-key', 'secret-key')

container = driver.get_container('container')

container.upload_object('test.txt', 'test.txt')
```

I am using Python 3.9.8-1 on Debian unstable with Libcloud 3.4.1.

libcloud/storage/drivers/s3.py の upload_object_via_stream()、_put_object_multipart()、_initiate_multipart() から始め、その経路を動作している upload_object() の経路と比較します。Aurora Objects の例を再現し、multipart 開始リクエストを追跡します。SignatureDoesNotMatch や InvalidCredsError が発生せずにストリーミングアップロードが成功すれば完了です。

索引モデルが issue の本文から書いたものです。