Delete SQS message if unmarshalling fails (#504)

* Delete SQS message if unmarshalling fails

* Fix failing unit test

Author: bharat-p

v1/brokers/sqs/sqs.go

@@ -205,6 +205,10 @@ func (b *Broker) consumeOne(delivery *awssqs.ReceiveMessageOutput, taskProcessor
 	decoder.UseNumber()
 	if err := decoder.Decode(sig); err != nil {
 		log.ERROR.Printf("unmarshal error. the delivery is %v", delivery)
+		// if the unmarshal fails, remove the delivery from the queue
+		if delErr := b.deleteOne(delivery); delErr != nil {
+			log.ERROR.Printf("error when deleting the delivery. delivery is %v, Error=%s", delivery, delErr)
+		}
 		return err
 	}
 	if delivery.Messages[0].ReceiptHandle != nil {