Log Message:
Update devel/kafka to 0.10.2.1

Improvement

- SCRAM secret's should be better protected with Zookeeper ACLs

Bug

- Refresh consumer metadata more frequently for unknown subscribed
  topics
- OffsetValidationTest fails validation with "Current position greater
  than the total number of consumed records"
- Failure in
  kafka/tests/kafkatest/tests/core/security_rolling_upgrade_test.py
- Broker level configuration 'log.segment.bytes' not used when
  'segment.bytes' not configured per topic.
- Kafka Streams - unable to add state stores when using wildcard
  topics on the source
- Streams State transition ASCII diagrams need fixing and polishing
- KafkaConsumer: ConsumerConfig gets logged twice.
- docker/run_tests.sh should set up /opt/kafka-dev to be the source
  directory
- Config validation in Connector plugins need to compare against both
  canonical and simple class names
- Stream thread getting into deadlock state while trying to get
  rocksdb lock in retryWithBackoff
- SessionStore.fetch(key) is a performance bottleneck
- log.message.timestamp.type=LogAppendTime breaks Kafka based
  consumers
- Querying window store may return unwanted keys
- Kafka Secure Migrator tool doesn't secure all the nodes
- Kafka Connect does not log connector configuration errors
- Make ProduceRequest thread-safe
- Add streams tests with brokers failing
- Document that stores must not be closed when Processors are closed
- remove controller concurrent access to non-threadsafe NetworkClient,
  Selector, and SSLEngine
- testReprocessingFromScratch unit test failure
- StreamThread should catch InvalidTopicException
- running multiple kafka streams instances causes one or more instance
  to get into file contention
- Increase number of Streams producer retries from the default of 0
- Defer exception to the next pollOnce() if consumer's fetch position
  has already increased
- ThreadCacheTest.cacheOverheadsSmallValues fails intermittently
- KafkaConsumer.poll throws IllegalStateException