SwiftService list in 3.13.1 throws "No tenant specified" on iterating with __iter__ through results

[David Lassig]

I tried to use the example in https://opendev.org/openstack/python-swiftclient/src/tag/3.13.1/examples/list.py with python-swiftclient in version 3.13.1

Converting to a minimal example to focus the bug:

```python
from swiftclient.client import Connection
from swiftclient.service import SwiftService

_authurl = XXX
_key = XXX
_tenant = 'my_tenant'

minimum_size = 10*1024**2

conn = Connection(
    preauthurl =_authurl,
    preauthtoken =_key,
    os_options = {"tenant_name":_tenant,
                  "tenant_id":_tenant,
                  }
)

resp_headers, containers = conn.get_account()
for container in containers:
    print(container)

with SwiftService() as swift:
    # works as expected
    list_parts_gen = swift.list(container=conn)
    next(list_parts_gen)

    # will raise error on iterating
    list_parts_gen = swift.list(container=conn)
    for list in list_parts_gen:
        print(list)
        break
```

On execution the __next__ on the iterator works as expected:

```json
{'bytes': 1522284, 'hash': 'e4076afb2c4eaa7722558f804c7ac069', 'name': 'Super Albar.stl', 'content_type': 'application/sla', 'last_modified': '2022-04-26T10:29:36.274230'}
```

But doing the same with __iter__ on the iterator raises:

```json
{'action': 'list_container_part', 'container': <swiftclient.client.Connection object at 0x7f2470045b20>, 'prefix': None, 'success': False, 'marker': '', 'version_marker': '', 'error': ClientException('No tenant specified'), 'traceback': 'Traceback (most recent call last):\n File "/usr/local/lib/python3.8/site-packages/swiftclient/service.py", line 1015, in _list_container_job\n _, items = conn.get_container(\n File "/usr/local/lib/python3.8/site-packages/swiftclient/client.py", line 1935, in get_container\n return self._retry(None, get_container, container, marker=marker,\n File "/usr/local/lib/python3.8/site-packages/swiftclient/client.py", line 1845, in _retry\n self.url, self.token = self.get_auth()\n File "/usr/local/lib/python3.8/site-packages/swiftclient/client.py", line 1789, in get_auth\n self.url, self.token = get_auth(self.authurl, self.user, self.key,\n File "/usr/local/lib/python3.8/site-packages/swiftclient/client.py", line 769, in get_auth\n raise ClientException(\'No tenant specified\')\nswiftclient.exceptions.ClientException: No tenant specified\n', 'error_timestamp': 1651140546.702744}
```

Actually the tenant is defined in the container object itself but much more important, there shouldn't a difference in handling the iterator with __next__ or __iter__. I tried to find the source for this problem but wasn't able to.

I tried to add in the SwiftService() object after initialization with the necessary `os_options` dict but this leads to Type error.