Fix processingTime update

Update the processingTime input metric only once after the for loop
using the time since processingStartTime.

Before this change, by updating processingStartTime inside the loop we
ended up counting time multiple times.

Author: zmoog

x-pack/filebeat/input/azureeventhub/v2_input.go

@@ -561,9 +561,11 @@ func (in *eventHubInputV2) processReceivedEvents(receivedEvents []*azeventhubs.R
 
 		// Update input metrics.
 		in.metrics.processedMessages.Inc()
-		in.metrics.processingTime.Update(time.Since(processingStartTime).Nanoseconds())
 	}
 
+	// Update input metrics.
+	in.metrics.processingTime.Update(time.Since(processingStartTime).Nanoseconds())
+
 	return nil
 }