New consumer times out joining group in consumer_test.py system test

The consumer_test.py system test fails with two different errors related to consumers joining the consumer group in a timely fashion.

• Consumers failed to join in a reasonable amount of time
• Timed out waiting for consumers to join, expected total X joined, but only see Y joined fromnormal consumer group and Z from conflict consumer group

Affected tests:

• test_fencing_static_consumer
• test_static_consumer_bounce
• test_static_consumer_persisted_after_rejoin