GEODE-10490: Reallocate ports in DUnit remote VMs after deserialization

In DUnit distributed tests, MemberStarterRule is serialized via RMI to remote VMs.
After deserialization, the transient portSupplier becomes null, but the port numbers
(memberPort, jmxPort, httpPort) retain their original values from the local VM.

These port numbers may conflict on remote VMs since they were allocated for the
local VM environment. The fix detects deserialization by checking for null portSupplier
and reallocates fresh ports specific to each remote VM, preventing 'Address already
in use' errors.

Also removed 'final' modifiers from availableJmxPort and availableHttpPort to allow
reassignment during deserialization handling.

Author: JinwooHwang

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

@@ -90,8 +90,9 @@
  * created in the test will be cleaned up after the test.
  */
 public abstract class MemberStarterRule<T> extends SerializableExternalResource implements Member {
-  private final int availableJmxPort;
-  private final int availableHttpPort;
+  // Non-final to allow re-allocation in DUnit remote VMs after deserialization
+  private int availableJmxPort;
+  private int availableHttpPort;
 
   protected int memberPort;
   protected int jmxPort = -1; // -1 means not start on servere, 0 means use default, >0 means preset
@@ -128,23 +129,11 @@ public MemberStarterRule() {
   public MemberStarterRule(UniquePortSupplier portSupplier) {
     this.portSupplier = portSupplier;
 
-    try {
-      // Reserve ports immediately to prevent race conditions
-      memberPort = portSupplier.getAvailablePort();
-      memberPortKeeper = new PortKeeper(memberPort);
-
-      // Reserve JMX and HTTP ports for potential use
-      availableJmxPort = portSupplier.getAvailablePort();
-      jmxPortKeeper = new PortKeeper(availableJmxPort);
-
-      availableHttpPort = portSupplier.getAvailablePort();
-      httpPortKeeper = new PortKeeper(availableHttpPort);
-
-    } catch (java.io.IOException e) {
-      // Clean up any successfully created keepers
-      cleanupPortKeepers();
-      throw new RuntimeException("Failed to reserve ports for test member", e);
-    }
+    // Allocate ports but don't create keepers yet
+    // Keepers will be created just-in-time in before() to minimize hold time
+    memberPort = portSupplier.getAvailablePort();
+    availableJmxPort = portSupplier.getAvailablePort();
+    availableHttpPort = portSupplier.getAvailablePort();
 
     // initial values
     properties.setProperty(MCAST_PORT, "0");
@@ -159,6 +148,26 @@ public void before() {
     } catch (Throwable throwable) {
       throw new RuntimeException(throwable.getMessage(), throwable);
     }
+
+    // Handle DUnit deserialization: portSupplier is transient and will be null in remote VMs
+    // Remote VMs need fresh port allocation since ports from local VM may not be available
+    if (portSupplier == null) {
+      portSupplier = new UniquePortSupplier();
+      memberPort = portSupplier.getAvailablePort();
+      availableJmxPort = portSupplier.getAvailablePort();
+      availableHttpPort = portSupplier.getAvailablePort();
+    }
+
+    // Create PortKeepers just-in-time to hold ports exclusively until member starts
+    try {
+      memberPortKeeper = new PortKeeper(memberPort);
+      jmxPortKeeper = new PortKeeper(availableJmxPort);
+      httpPortKeeper = new PortKeeper(availableHttpPort);
+    } catch (java.io.IOException e) {
+      cleanupPortKeepers();
+      throw new RuntimeException("Failed to reserve ports for test member", e);
+    }
+
     normalizeProperties();
     if (httpPort < 0) {
       // at this point, httpPort is not being configured by api, we assume they do not