CID v1 retrieved from client.add is different with the CID retrieved from IPFS API or CLI

## Problem

The CID v1 retrieved using the ipfshttpclient is different with the CID retrieved using IPFS HTTP API or CLI directly.

## Environment

OS: `Ubuntu 20.04`
Python version: `3.8.5`
Package version: `ipfshttpclient==0.8.0a2`
ipfs version: `0.8.0`

## Minimal code to reproduce the problem

Using an empty file to reproduce the problem. The problem is also reproducible using any file.

```python3
>>> import io
>>> import ipfshttpclient
>>> host_addr = '/dns4/localhost/tcp/5001/http'
>>> client = ipfshttpclient.connect(host_addr)

>>> file_object = io.BytesIO(b'')
>>> client.add(file_object, opts={'cid-version': 1})

```

```python3
>>> import io
>>> import requests
>>> url = 'http://localhost:5001/api/v0/add'
>>> params = {'cid-version': 1}

>>> file_object = io.BytesIO(b'')
>>> requests.post(url, params=params, files={'file': file_object})
{'Name': 'file', 'Hash': 'bafkreihdwdcefgh4dqkjv67uzcmw7ojee6xedzdetojuzjevtenxquvyku', 'Size': '0'}
```

```bash
$ touch empty
$ ipfs add --cid-version 1 empty
added bafkreihdwdcefgh4dqkjv67uzcmw7ojee6xedzdetojuzjevtenxquvyku empty
```

As seen in the response, the response get from using ipfshttpclient has different CID from the one get using HTTP API or CLI. Also, the size should actually be `0`, not `6`.
If using a file with some content (not empty), the size difference could be observed as well.