PublishKafkaRecord_2_6 - RoundRobin partitioner skipping every other partition

When configured to use the NiFi RoundRobin partitioner, the processor publishes to every other partition. If the number of partitions in the topic and the number of records being published are the right combination, this problem is masked. We see this issue when we set the partitions to 26, but not when set to 25. 

I took a code-dive into the o.a.k.c.producer.KafkaProducer and discovered that it is invoking the Partitioner twice when a "new batch" is created. Thus, the RoundRobin partitioner bumps the index by 2. If the RoundRobin partitioner overwrote the onNewBatch method, this problem could be solved.