title: KafkaConsumer polling issue
body: <p>I am trying to implement a Kafka consumer using Kotlin co-routines. I have placed the consumer <code>poll()</code> function inside the co-routine. For reading from multiple partitions, I have run two consumers subscribed to same topic with same group-id. The actual problem is that, the consumer <code>poll()</code> is turning into a long running function and hence utilizing all the worker threads.</p>
  
  <p>The issue is only when I run two consumers with same group-id. When I run consumers with different group-id, there won't be such issue.</p>