processstreamwithcachedstatestore and other streams benchmarks fail occasionally

test_id: kafkatest.benchmarks.streams.streams_simple_benchmark_test.StreamsSimpleBenchmarkTest.test_simple_benchmark.test=processstreamwithcachedstatestore.scale=2
status: FAIL
run time: 14 minutes 58.069 seconds

Streams Test process on ubuntu@worker5 took too long to exit
Traceback (most recent call last):
File "/var/lib/jenkins/workspace/system-test-kafka/kafka/venv/local/lib/python2.7/site-packages/ducktape-0.6.0-py2.7.egg/ducktape/tests/runner_client.py", line 123, in run
data = self.run_test()
File "/var/lib/jenkins/workspace/system-test-kafka/kafka/venv/local/lib/python2.7/site-packages/ducktape-0.6.0-py2.7.egg/ducktape/tests/runner_client.py", line 176, in run_test
return self.test_context.function(self.test)
File "/var/lib/jenkins/workspace/system-test-kafka/kafka/venv/local/lib/python2.7/site-packages/ducktape-0.6.0-py2.7.egg/ducktape/mark/_mark.py", line 321, in wrapper
return functools.partial(f, *args, **kwargs)(*w_args, **w_kwargs)
File "/var/lib/jenkins/workspace/system-test-kafka/kafka/tests/kafkatest/benchmarks/streams/streams_simple_benchmark_test.py", line 86, in test_simple_benchmark
self.driver[num].wait()
File "/var/lib/jenkins/workspace/system-test-kafka/kafka/tests/kafkatest/services/streams.py", line 102, in wait
self.wait_node(node, timeout_sec)
File "/var/lib/jenkins/workspace/system-test-kafka/kafka/tests/kafkatest/services/streams.py", line 106, in wait_node
wait_until(lambda: not node.account.alive(pid), timeout_sec=timeout_sec, err_msg="Streams Test process on " + str(node.account) + " took too long to exit")
File "/var/lib/jenkins/workspace/system-test-kafka/kafka/venv/local/lib/python2.7/site-packages/ducktape-0.6.0-py2.7.egg/ducktape/utils/util.py", line 36, in wait_until
raise TimeoutError(err_msg)
TimeoutError: Streams Test process on ubuntu@worker5 took too long to exit

The log contains several lines like:
[2017-03-11 04:52:59,080] DEBUG Attempt to heartbeat failed for group simple-benchmark-streams-with-storetrue since it is rebalancing. (org.apache.kafka.clients.consumer.internals.AbstractCoordinator)
[2017-03-11 04:53:01,987] DEBUG Sending Heartbeat request for group simple-benchmark-streams-with-storetrue to coordinator worker10:9092 (id: 2147483646 rack: null) (org.apache.kafka.clients.consumer.internals.AbstractCoordinator)
[2017-03-11 04:53:02,088] DEBUG Attempt to heartbeat failed for group simple-benchmark-streams-with-storetrue since it is rebalancing. (org.apache.kafka.clients.consumer.internals.AbstractCoordinator)
[2017-03-11 04:53:04,995] DEBUG Sending Heartbeat request for group simple-benchmark-streams-with-storetrue to coordinator worker10:9092 (id: 2147483646 rack: null) (org.apache.kafka.clients.consumer.internals.AbstractCoordinator)

Other tests that fail the same way include:
test_id: kafkatest.benchmarks.streams.streams_simple_benchmark_test.StreamsSimpleBenchmarkTest.test_simple_benchmark.test=count.scale=2
test_id: kafkatest.benchmarks.streams.streams_simple_benchmark_test.StreamsSimpleBenchmarkTest.test_simple_benchmark.test=processstreamwithsink.scale=1
test_id: kafkatest.tests.streams.streams_bounce_test.StreamsBounceTest.test_bounce