GEODE-10490: Fix PortKeeper serialization for DUnit tests

- Made PortKeeper fields transient in MemberStarterRule
- Made UniquePortSupplier transient to avoid RMI serialization
- Added PortKeeper to HeadlessGfshIntegrationTest for port reservation
- Prevents NotSerializableException in distributed tests
- Fixes DUnit test failures (RegisterDriverCommandDUnitTest, MemberManagementServiceRestDUnitTest, etc)

Author: JinwooHwang

geode-dunit/src/main/java/org/apache/geode/test/junit/rules/MemberStarterRule.java

@@ -104,11 +104,11 @@ public abstract class MemberStarterRule<T> extends SerializableExternalResource
 
   protected boolean autoStart = false;
 
-  // Port keepers for zero-gap port reservation
-  protected PortKeeper memberPortKeeper;
-  protected PortKeeper jmxPortKeeper;
-  protected PortKeeper httpPortKeeper;
-  private UniquePortSupplier portSupplier;
+  // Port keepers for zero-gap port reservation (transient to avoid RMI serialization in DUnit)
+  protected transient PortKeeper memberPortKeeper;
+  protected transient PortKeeper jmxPortKeeper;
+  protected transient PortKeeper httpPortKeeper;
+  private transient UniquePortSupplier portSupplier;
 
   private List<File> firstLevelChildrenFile = new ArrayList<>();
   private boolean cleanWorkingDir = true;

geode-gfsh/src/integrationTest/java/org/apache/geode/management/internal/cli/HeadlessGfshIntegrationTest.java

@@ -43,13 +43,15 @@
 import org.apache.geode.management.cli.Result;
 import org.apache.geode.management.internal.cli.result.CommandResult;
 import org.apache.geode.test.junit.categories.GfshTest;
+import org.apache.geode.test.junit.rules.PortKeeper;
 
 /**
  * TODO : Add more tests for error-catch, different type of results etc
  */
 @Category({GfshTest.class})
 public class HeadlessGfshIntegrationTest {
   private int port;
+  private PortKeeper jmxPortKeeper;
   private DistributedSystem ds;
   private GemFireCacheImpl cache;
   private HeadlessGfsh gfsh;
@@ -63,6 +65,7 @@ public class HeadlessGfshIntegrationTest {
   @Before
   public void setup() throws IOException {
     port = getRandomAvailableTCPPort();
+    jmxPortKeeper = new PortKeeper(port);
 
     Properties properties = new Properties();
     properties.put(NAME, testName.getMethodName());
@@ -72,6 +75,7 @@ public void setup() throws IOException {
     properties.put(HTTP_SERVICE_PORT, "0");
     properties.put(MCAST_PORT, "0");
 
+    jmxPortKeeper.close(); // Release port immediately before binding
     legacyConnect(properties);
 
     gfsh = new HeadlessGfsh("Test", 25,