MINOR: Move log statement stating producer closed after possible exception (#6606)

In the KafkaProducer#close method we have a debug log statement Kafka producer has been closed then a few lines later a KafkaException can occur.
This could be confusing to users, so this PR simply moves the log statement to after the possible exception to avoid confusing information in the logs.

Reviewers:  Guozhang Wang <wangguoz@gmail.com>

clients/src/main/java/org/apache/kafka/clients/producer/KafkaProducer.java

@@ -1189,7 +1189,6 @@ public class KafkaProducer<K, V> implements Producer<K, V> {
         ClientUtils.closeQuietly(valueSerializer, "producer valueSerializer", firstException);
         ClientUtils.closeQuietly(partitioner, "producer partitioner", firstException);
         AppInfoParser.unregisterAppInfo(JMX_PREFIX, clientId, metrics);
-        log.debug("Kafka producer has been closed");
         Throwable exception = firstException.get();
         if (exception != null && !swallowException) {
             if (exception instanceof InterruptException) {
@@ -1197,6 +1196,7 @@ public class KafkaProducer<K, V> implements Producer<K, V> {
             }
             throw new KafkaException("Failed to close kafka producer", exception);
         }
+        log.debug("Kafka producer has been closed");
     }
 
     private static Map<String, Object> propsToMap(Properties properties) {