node-proxy: fix a regression when processing the RedFish API

node-proxy: fix a regression when processing the RedFish API

ce360a4a5f6 introduced a regression.

`Endpoint()` doesn't take a `EndpointMgr` object as parameter.
The call `e = Endpoint(self, _url, self.client)` obviously throws the
following error:

```
TypeError: __init__() takes 3 positional arguments but 4 were given
```

This commit fixes it.

Fixes: https://tracker.ceph.com/issues/68231
Signed-off-by: Guillaume Abrioux <gabrioux@ibm.com>
(cherry picked from commit ad0a7fa655e525194e1099a66907a691a3e5e2cf)