Fix messaging tracing. Injecting trace data after json serializing fa…

…iled; inject prior to serializing. (#119)

Signed-off-by: Mike Kingsbury <[email protected]>

resultsdb/messaging.py

@@ -213,11 +213,12 @@ def __init__(self, **kwargs):
                 raise ValueError(f"Missing {attr!r} option for STOMP messaging plugin")
 
     def publish(self, msg):
-        msg = json.dumps(msg)
         # Add telemetry information. This includes an extra key
         # traceparent.
         TraceContextTextMapPropagator().inject(msg)
 
+        msg = json.dumps(msg)
+
         kwargs = dict(body=msg, headers={}, destination=self.destination)
 
         conn = stomp.connect.StompConnection11(**self.connection)