Fix task manager tests, use reserved port range (#81979) (#81988)

TransportTasksActionTests#testFailedTasksCount would rarely fail, with
symptoms looking like an external client connecting and doing a
handshake. Now switch to using the test worker specific port range.

Relates #69731

server/src/test/java/org/elasticsearch/action/admin/cluster/node/tasks/TaskManagerTestCase.java

@@ -40,6 +40,7 @@
 import org.elasticsearch.threadpool.TestThreadPool;
 import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.transport.TransportService;
+import org.elasticsearch.transport.TransportSettings;
 import org.elasticsearch.transport.nio.MockNioTransport;
 import org.junit.After;
 import org.junit.Before;
@@ -78,8 +79,12 @@ public void setupTestNodes(Settings settings) {
     public void setupTestNodes(Settings settings, Version version) {
         nodesCount = randomIntBetween(2, 10);
         testNodes = new TestNode[nodesCount];
+        final Settings reservedPortRangeSettings = Settings.builder()
+            .put(TransportSettings.PORT.getKey(), getPortRange())
+            .put(settings)
+            .build();
         for (int i = 0; i < testNodes.length; i++) {
-            testNodes[i] = new TestNode("node" + i, threadPool, version, settings);
+            testNodes[i] = new TestNode("node" + i, threadPool, version, reservedPortRangeSettings);
         }
     }