Speed up observation startup

tangostationcontrol/tangostationcontrol/devices/observation_control.py

@@ -151,7 +151,11 @@ class ObservationControl(LOFARDevice):
         """Callback for when an observation is started, use to emit metadata"""
 
         try:
-            self.metadata.send_metadata()
+            logger.info("Triggering metadata update")
+
+            # trigger asynchronous call, we do not care about the result,
+            # since we cannot afford to wait delaying the observation setup
+            self.metadata.command_inout_asynch("send_metadata", None, True)
         except Exception as e:
             logger.exception(
                 f"Observation start callback for observation {observation_id} "