Use test cluster exclusive in CancellableTasksIT (#67058)

testRemoveBanParentsOnDisconnect disconnects some nodes and leaves the 
cluster in an unhealthy state, which fails other tests. We can reconnect
nodes after that test. However, this commit chooses to run this suite
test-cluster exclusive instead because it is simpler and more stable.

Closes #6652

server/src/internalClusterTest/java/org/elasticsearch/action/admin/cluster/node/tasks/CancellableTasksIT.java

@@ -60,7 +60,6 @@ import org.elasticsearch.transport.TransportException;
 import org.elasticsearch.transport.TransportResponseHandler;
 import org.elasticsearch.transport.TransportService;
 import org.junit.After;
-import org.junit.Before;
 
 import java.io.IOException;
 import java.util.ArrayList;
@@ -83,6 +82,7 @@ import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.hasSize;
 import static org.hamcrest.Matchers.instanceOf;
 
+@ESIntegTestCase.ClusterScope(scope = ESIntegTestCase.Scope.TEST)
 public class CancellableTasksIT extends ESIntegTestCase {
 
     static int idGenerator = 0;
@@ -91,15 +91,6 @@ public class CancellableTasksIT extends ESIntegTestCase {
     static final Map<TestRequest, CountDownLatch> beforeExecuteLatches = ConcurrentCollections.newConcurrentMap();
     static final Map<TestRequest, CountDownLatch> completedLatches = ConcurrentCollections.newConcurrentMap();
 
-    @Before
-    public void resetTestStates() {
-        idGenerator = 0;
-        beforeSendLatches.clear();
-        arrivedLatches.clear();
-        beforeExecuteLatches.clear();
-        completedLatches.clear();
-    }
-
     @After
     public void ensureAllBansRemoved() throws Exception {
         assertBusy(() -> {
@@ -150,7 +141,7 @@ public class CancellableTasksIT extends ESIntegTestCase {
             beforeSendLatches.get(req).countDown();
         }
         for (TestRequest req : sentRequests) {
-            arrivedLatches.get(req).await();
+            assertTrue(arrivedLatches.get(req).await(60, TimeUnit.SECONDS));
         }
         Set<TestRequest> completedRequests = new HashSet<>();
         for (TestRequest req : randomSubsetOf(sentRequests)) {
@@ -163,7 +154,7 @@ public class CancellableTasksIT extends ESIntegTestCase {
             beforeExecuteLatches.get(req).countDown();
         }
         for (TestRequest req : completedRequests) {
-            completedLatches.get(req).await();
+            assertTrue(completedLatches.get(req).await(60, TimeUnit.SECONDS));
         }
         return Sets.difference(sentRequests, completedRequests);
     }
@@ -500,7 +491,7 @@ public class CancellableTasksIT extends ESIntegTestCase {
             GroupedActionListener<TestResponse> groupedListener =
                 new GroupedActionListener<>(listener.map(r -> new TestResponse()), subRequests.size() + 1);
             transportService.getThreadPool().generic().execute(ActionRunnable.supply(groupedListener, () -> {
-                beforeExecuteLatches.get(request).await();
+                assertTrue(beforeExecuteLatches.get(request).await(60, TimeUnit.SECONDS));
                 if (((CancellableTask) task).isCancelled()) {
                     throw new TaskCancelledException("Task was cancelled while executing");
                 }
@@ -524,7 +515,7 @@ public class CancellableTasksIT extends ESIntegTestCase {
 
                 @Override
                 protected void doRun() throws Exception {
-                    beforeSendLatches.get(subRequest).await();
+                    assertTrue(beforeSendLatches.get(subRequest).await(60, TimeUnit.SECONDS));
                     if (client.getLocalNodeId().equals(subRequest.node.getId()) && randomBoolean()) {
                         try {
                             client.executeLocally(TransportTestAction.ACTION, subRequest, latchedListener);