MINOR: fix DynamicBrokerReconfigurationTest (#22226)

The test is subject to a race-condition. This PR change async to sync
call to fix it.

Reviewers: Chia-Ping Tsai <chia7712@gmail.com>

Author: mjsax

core/src/test/scala/integration/kafka/server/DynamicBrokerReconfigurationTest.scala

@@ -1262,7 +1262,18 @@ class DynamicBrokerReconfigurationTest extends QuorumTestHarness with SaslSetup
   }
 
   private def alterConfigs(servers: Seq[KafkaBroker], adminClient: Admin, props: Properties,
-                   perBrokerConfig: Boolean): AlterConfigsResult = {
+                           perBrokerConfig: Boolean): Unit = {
+    alterConfigsAsync(servers, adminClient, props, perBrokerConfig).all.get()
+    // Skip config-provider placeholders (e.g. "${file:...}"): the broker stores the resolved value,
+    // so waiting on the literal placeholder would never match. Callers using placeholders must wait
+    // on the resolved value themselves.
+    props.asScala.foreach { case (k, v) =>
+      if (!v.contains("${")) waitForConfig(k, v)
+    }
+  }
+
+  private def alterConfigsAsync(servers: Seq[KafkaBroker], adminClient: Admin, props: Properties,
+                                perBrokerConfig: Boolean): AlterConfigsResult = {
     val configEntries = props.asScala.map { case (k, v) => new AlterConfigOp(new ConfigEntry(k, v), OpType.SET) }.toList.asJava
     val configs = if (perBrokerConfig) {
       val alterConfigs = new java.util.HashMap[ConfigResource, java.util.Collection[AlterConfigOp]]()
@@ -1277,7 +1288,7 @@ class DynamicBrokerReconfigurationTest extends QuorumTestHarness with SaslSetup
   }
 
   private def reconfigureServers(newProps: Properties, perBrokerConfig: Boolean, aPropToVerify: (String, String), expectFailure: Boolean = false): Unit = {
-    val alterResult = alterConfigs(servers, adminClients.head, newProps, perBrokerConfig)
+    val alterResult = alterConfigsAsync(servers, adminClients.head, newProps, perBrokerConfig)
     if (expectFailure) {
       val oldProps = servers.head.config.values.asScala.filter { case (k, _) => newProps.containsKey(k) }
       val brokerResources = if (perBrokerConfig)