Critical Description
https://issues.apache.org/jira/browse/KAFKA-10866 added metadata to ConsumerRecords. We add metadata even when there are no records. As a result, we sometimes return early from KafkaConsumer#poll() with no records because FetchedRecords.isEmpty returns false if either metadata or records are available. This breaks system tests which rely on poll timeout, expecting records to be returned on every poll when there is no timeout.