MINOR: ensure KafkaServerTestHarness::tearDown is always invoked (#15996)

An exception thrown while closing the client instances in `IntegrationTestHarness::tearDown` may result in `KafkaServerTestHarness::tearDown` not being invoked. This would result in thread leaks of the broker and controller threads spawned in the failing test.

An example of this is the [CI run](https://ci-builds.apache.org/blue/organizations/jenkins/Kafka%2Fkafka-pr/detail/PR-15994/1/tests) for #15994 where `Build / JDK 8 and Scala 2.12 / testCoordinatorFailover(String, String).quorum=kraft+kip848.groupProtocol=consumer – kafka.api.PlaintextConsumerTest` failing results in `consumers.foreach(_.close(Duration.ZERO))` in `IntegrationTestHarness::tearDown` throwing an exception.

A side effect of this is it poisons Gradle test runner JVM and prevents tests in other unrelated classes from executing as `@BeforeAll` check in QuorumTestHarness would cause them to fail immediately.

This PR encloses the client closure in try-finally to ensure`KafkaServerTestHarness::tearDown` is always invoked.

Reviewers: Nikhil Ramakrishnan <nikrmk@amazon.com>, Igor Soarez <soarez@apple.com>, Chia-Ping Tsai <chia7712@gmail.com>

core/src/test/scala/integration/kafka/api/IntegrationTestHarness.scala

@@ -220,6 +220,7 @@ abstract class IntegrationTestHarness extends KafkaServerTestHarness {
 
   @AfterEach
   override def tearDown(): Unit = {
+    try {
       producers.foreach(_.close(Duration.ZERO))
       consumers.foreach(_.wakeup())
       consumers.foreach(_.close(Duration.ZERO))
@@ -228,8 +229,9 @@ abstract class IntegrationTestHarness extends KafkaServerTestHarness {
       producers.clear()
       consumers.clear()
       adminClients.clear()
-
+    } finally {
       super.tearDown()
     }
+  }
 
 }