@Override
        public void onComplete(Map<TopicPartition, OffsetAndMetadata> offsets, Exception exception) {
            invoked++;
            this.exception = exception;
        }
Verifies that subscription change updates SubscriptionState correctly even after JoinGroup failures
that don't re-invoke onJoinPrepare.
clients/src/test/java/org/apache/kafka/clients/consumer/internals/ConsumerCoordinatorTest.java