CreateBucket throws BucketAlreadyOwnedByYou exception

From a jenkins e2e test:

```
Traceback (most recent call last):
File "/tmp/workspace/libcloudforensics-e2e-aws/libcloudforensics/providers/aws/internal/s3.py", line 94, in CreateBucket
bucket = client.create_bucket(
File "/usr/local/lib/python3.8/dist-packages/botocore/client.py", line 401, in _api_call
return self._make_api_call(operation_name, kwargs)
File "/usr/local/lib/python3.8/dist-packages/botocore/client.py", line 731, in _make_api_call
raise error_class(parsed_response, operation_name)
botocore.errorfactory.BucketAlreadyOwnedByYou: An error occurred (BucketAlreadyOwnedByYou) when calling the CreateBucket operation: Your previous request to create the named bucket succeeded and you already own it.
```

If the bucket exists and is already owned by the user, we probably shouldn't throw an error but allow them to continue. We can return a `created` value to indicate whether the bucket was created or already existed.