Fix bug with **kwargs and kafka kwarg

gwcelery/kafka/bootsteps.py

@@ -35,7 +35,7 @@ class Producer(KafkaBootStep):
 
     name = 'Kafka Avro producer'
 
-    def __init__(self, parent, kafka=False, **kwargs):
+    def __init__(self, parent, **kwargs):
         super().__init__(parent, **kwargs)
         self.topic_url = parent.app.conf['scimma_broker_url'] + \
             parent.app.conf['scimma_topic_name']