[Test] Allow leader/follower checks in pending tasks (#123841)

Leader and follower checks are expected to run regularly for any
multi-node clusters. This PR allows them to be observed in the list of
tasks during cleanup phase of REST tests.

Author: ywangd

server/src/main/java/org/elasticsearch/cluster/coordination/LeaderChecker.java

@@ -60,7 +60,7 @@ public class LeaderChecker {
 
     private static final Logger logger = LogManager.getLogger(LeaderChecker.class);
 
-    static final String LEADER_CHECK_ACTION_NAME = "internal:coordination/fault_detection/leader_check";
+    public static final String LEADER_CHECK_ACTION_NAME = "internal:coordination/fault_detection/leader_check";
 
     // the time between checks sent to the leader
     public static final Setting<TimeValue> LEADER_CHECK_INTERVAL_SETTING = Setting.timeSetting(

test/framework/src/main/java/org/elasticsearch/test/rest/ESRestTestCase.java

@@ -134,6 +134,8 @@
 import static java.util.Collections.unmodifiableList;
 import static org.elasticsearch.client.RestClient.IGNORE_RESPONSE_CODES_PARAM;
 import static org.elasticsearch.cluster.ClusterState.VERSION_INTRODUCING_TRANSPORT_VERSIONS;
+import static org.elasticsearch.cluster.coordination.FollowersChecker.FOLLOWER_CHECK_ACTION_NAME;
+import static org.elasticsearch.cluster.coordination.LeaderChecker.LEADER_CHECK_ACTION_NAME;
 import static org.elasticsearch.core.Strings.format;
 import static org.elasticsearch.test.MapMatcher.assertMap;
 import static org.elasticsearch.test.MapMatcher.matchesMap;
@@ -677,6 +679,8 @@ public static void waitForPendingTasks(final RestClient restClient, final Predic
                             final String taskName = line.split("\\s+")[0];
                             if (taskName.startsWith(TransportListTasksAction.TYPE.name())
                                 || taskName.startsWith(HealthNode.TASK_NAME)
+                                || taskName.startsWith(LEADER_CHECK_ACTION_NAME)
+                                || taskName.startsWith(FOLLOWER_CHECK_ACTION_NAME)
                                 || taskFilter.test(taskName)) {
                                 continue;
                             }