SQSMessageConsumerPrefetch keeps fetching messages after stop

[XakepSDK]

1. We have TestA: this test sends the message in the testAQueue, and checks some response after it was processed
2. We have TestB: this test invokes http endpoint and waits for the message in the testAQueue

When we run TestA, we start JMS Listener for the testAQueue. After the test, we stop the listener
When we run TestB, sometimes message in the testAQueue does not appear immediately, but appears after WAIT_TIME_SECONDS
Both tests should run one after another.

After some debugging, it appears that SQSMessageConsumerPrefetch tries to fetch the message even when running = false
I've put a non-suspending breakpoint here: https://github.com/awslabs/amazon-sqs-java-messaging-lib/blob/master/src/main/java/com/amazon/sqs/javamessaging/SQSMessageConsumerPrefetch.java#L261
to print the state of the running flag. When the error I've described is hit, the flag running is in false state.