cdc,tests: unit test kafkaSuite.TestNewSaramaProducer is flaky

[pingyu]

Bug Report

1. Describe the bug

=== FAIL: cdc/sink/producer/kafka Test (60.61s)

----------------------------------------------------------------------
FAIL: kafka_test.go:65: kafkaSuite.TestNewSaramaProducer

kafka_test.go:167:
    c.Assert(err, check.IsNil)
... value *errors.withStack = [CDC:ErrKafkaSendMessage]kafka send message failed: kafka: Failed to deliver 2 messages. ("[CDC:ErrKafkaSendMessage]kafka send message failed: kafka: Failed to deliver 2 messages.")

[2024/01/03 23:44:01.375 +08:00] [ERROR] [kafka.go:222] ["close async client with error"] [error="kafka: Failed to deliver 1 messages."] [stack="github.com/tikv/migration/cdc/cdc/sink/producer/kafka.(*kafkaSaramaProducer).Close\n\t/home/jenkins/agent/workspace/tikv/migration/pull_unit_test/migration/cdc/cdc/sink/producer/kafka/kafka.go:222\ngithub.com/tikv/migration/cdc/cdc/sink/producer/kafka.(*kafkaSuite).TestProducerSendMessageFailed.func4\n\t/home/jenkins/agent/workspace/tikv/migration/pull_unit_test/migration/cdc/cdc/sink/producer/kafka/kafka_test.go:364\ngithub.com/tikv/migration/cdc/cdc/sink/producer/kafka.(*kafkaSuite).TestProducerSendMessageFailed\n\t/home/jenkins/agent/workspace/tikv/migration/pull_unit_test/migration/cdc/cdc/sink/producer/kafka/kafka_test.go:397\nreflect.Value.call\n\t/usr/local/go/src/reflect/value.go:596\nreflect.Value.Call\n\t/usr/local/go/src/reflect/value.go:380\ngithub.com/pingcap/check.(*suiteRunner).forkTest.func1\n\t/go/pkg/mod/github.com/pingcap/check@v0.0.0-20211026125417-57bd13f7b5f0/check.go:850\ngithub.com/pingcap/check.(*suiteRunner).forkCall.func1\n\t/go/pkg/mod/github.com/pingcap/check@v0.0.0-20211026125417-57bd13f7b5f0/check.go:739"]

OOPS: 8 passed, 1 FAILED

See https://do.pingcap.net/jenkins/blue/organizations/jenkins/tikv%2Fmigration%2Fpull_unit_test/detail/pull_unit_test/16/pipeline.

2. Minimal reproduce step (Required)

Run unit tests in CI.

3. What did you see instead (Required)

Test failed.

4. What did you expect to see? (Required)

Test succeed.

5. What is your migration tool and TiKV version? (Required)

• TiKV: N/A
• TiKV CDC: [close #381] Add integration tests for Kafka sink #382, 4d33975
• TiKV BR:
• TiKV Online Bulk Load:

[pingyu]

Duplicated with #388