[fix][test] Fix flaky ConsumerBatchReceiveTest.testBatchReceiveAndRedeliveryNonPartitionedTopic

[merlimat]

Motivation

ConsumerBatchReceiveTest.testBatchReceiveAndRedeliveryNonPartitionedTopic is flaky due to two issues:

1. consumer.acknowledge(messages) is called outside the null check, causing NPE when batchReceive() returns null
2. Strict equality assertion fails because ack timeout redelivery can cause extra messages beyond the expected count

Stack trace

ConsumerBatchReceiveTest > testBatchReceiveAndRedeliveryNonPartitionedTopic[54] FAILED
    java.lang.AssertionError: expected [202] but found [200]
        at org.testng.Assert.fail(Assert.java:110)
        at org.testng.Assert.failNotEquals(Assert.java:1577)
        at org.testng.Assert.assertEqualsImpl(Assert.java:149)
        at org.testng.Assert.assertEquals(Assert.java:131)
        at ConsumerBatchReceiveTest.batchReceiveAndRedelivery(ConsumerBatchReceiveTest.java:635)

Modifications

• Move consumer.acknowledge(messages) inside the if (messages != null) block
• Change assertEquals(expected * 2, messageReceived) to assertTrue(messageReceived >= expected * 2) since redelivery can produce extra messages

Documentation

• doc-not-needed