cephadm: have agent check for errors before json loading mgr response

Currently, since it tries to json.loads the response
payload before checking the return code, if there was
an error it fails with

Failed to send metadata to mgr: the JSON object must be str, bytes or bytearray, not ConnectionRefusedError

which is masking the actual failure.

Also adds more context to the RuntimeError raised

Fixes: https://tracker.ceph.com/issues/65553

Signed-off-by: Adam King <[email protected]>

Author: adk3798

src/cephadm/cephadm.py

@@ -1577,10 +1577,10 @@ def run(self) -> None:
                                               data=data,
                                               endpoint='/data',
                                               ssl_ctx=self.ssl_ctx)
-                response_json = json.loads(response)
                 if status != 200:
                     logger.error(f'HTTP error {status} while querying agent endpoint: {response}')
-                    raise RuntimeError
+                    raise RuntimeError(f'non-200 response <{status}> from agent endpoint: {response}')
+                response_json = json.loads(response)
                 total_request_time = datetime.timedelta(seconds=(time.monotonic() - send_time)).total_seconds()
                 logger.info(f'Received mgr response: "{response_json["result"]}" {total_request_time} seconds after sending request.')
             except Exception as e: