Ensure setup is only called once

Closes #5857

Author: ahus1

vertx-core/src/test/java/io/vertx/tests/eventbus/VirtualThreadEventBusTest.java

@@ -22,7 +22,7 @@ public class VirtualThreadEventBusTest extends VertxTestBase {
 
   VertxInternal vertx;
 
-  @Before
+  @Override
   public void setUp() throws Exception {
     super.setUp();
     vertx = (VertxInternal) super.vertx;

vertx-core/src/test/java/io/vertx/tests/net/NetBandwidthLimitingTest.java

@@ -51,7 +51,7 @@ public class NetBandwidthLimitingTest extends VertxTestBase {
   private NetClient client = null;
   private final List<NetServer> servers = Collections.synchronizedList(new ArrayList<>());
 
-  @Before
+  @Override
   public void setUp() throws Exception {
     super.setUp();
     if (USE_DOMAIN_SOCKETS) {

vertx-core/src/test/java/io/vertx/tests/virtualthread/VirtualThreadContextTest.java

@@ -37,7 +37,7 @@ public class VirtualThreadContextTest extends VertxTestBase {
 
   VertxInternal vertx;
 
-  @Before
+  @Override
   public void setUp() throws Exception {
     super.setUp();
     vertx = (VertxInternal) super.vertx;