Do not parse the backend URL early

It may contain sharding tokens ('%s'), which confuse the urllib3
parser needlessly.

ai_web_common/rpc/core.py

@@ -172,9 +172,6 @@ class ClientStub():
         if 'url' not in backend:
             raise ValueError('backend spec does not contain "url"')
         self._url = backend['url'].rstrip('/')
-        parsed_url = urllib3.util.parse_url(self._url)
-        self._host = parsed_url.host
-        self._port = parsed_url.port
         self._sso_service = backend.get('sso_service')
         self._sso_exchange = sso_exchange