no need to check recv_callback_ after init
no need to check recv_callback_ after init

alfred-landrum/node-kafka-native,alfred-landrum/node-kafka-native,jut-io/node-kafka-native,jut-io/node-kafka-native,jut-io/node-kafka-native,jut-io/node-kafka-native,alfred-landrum/node-kafka-native,jut-io/node-kafka-native,alfred-landrum/node-kafka-native,alfred-landrum/node-kafka-native