[MINOR] fix: Add method close for ApplicationManager (#704)

### What changes were proposed in this pull request?
Add  method `close` for ApplicationManager

### Why are the changes needed?
Clean resources while testing. It will improve the stability of our test.

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?
GA passed

coordinator/src/main/java/org/apache/uniffle/coordinator/ApplicationManager.java

@@ -17,6 +17,7 @@
 
 package org.apache.uniffle.coordinator;
 
+import java.io.Closeable;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.util.Arrays;
@@ -46,7 +47,7 @@
 import org.apache.uniffle.coordinator.strategy.storage.SelectStorageStrategy;
 import org.apache.uniffle.coordinator.util.CoordinatorUtils;
 
-public class ApplicationManager {
+public class ApplicationManager implements Closeable {
 
   private static final Logger LOG = LoggerFactory.getLogger(ApplicationManager.class);
   // TODO: Add anomaly detection for other storage
@@ -62,6 +63,7 @@ public class ApplicationManager {
   private final Map<String, String> remoteStorageToHost = Maps.newConcurrentMap();
   private final Map<String, RemoteStorageInfo> availableRemoteStorageInfo;
   private final ScheduledExecutorService detectStorageScheduler;
+  private final ScheduledExecutorService checkAppScheduler;
   private Map<String, Map<String, Long>> currentUserAndApp = Maps.newConcurrentMap();
   private Map<String, String> appIdToUser = Maps.newConcurrentMap();
   private QuotaManager quotaManager;
@@ -93,9 +95,9 @@ public ApplicationManager(CoordinatorConf conf) {
       }
     }
     // the thread for checking application status
-    ScheduledExecutorService scheduledExecutorService = Executors.newSingleThreadScheduledExecutor(
+    checkAppScheduler = Executors.newSingleThreadScheduledExecutor(
         ThreadUtils.getThreadFactory("ApplicationManager-%d"));
-    scheduledExecutorService.scheduleAtFixedRate(
+    checkAppScheduler.scheduleAtFixedRate(
         this::statusCheck, expired / 2, expired / 2, TimeUnit.MILLISECONDS);
     // the thread for checking if the storage is normal
     detectStorageScheduler = Executors.newSingleThreadScheduledExecutor(
@@ -350,6 +352,15 @@ public static List<String> getPathSchema() {
     return REMOTE_PATH_SCHEMA;
   }
 
+  public void close() {
+    if (detectStorageScheduler != null) {
+      detectStorageScheduler.shutdownNow();
+    }
+    if (checkAppScheduler != null) {
+      checkAppScheduler.shutdownNow();
+    }
+  }
+
   public enum StrategyName {
     APP_BALANCE,
     IO_SAMPLE

coordinator/src/main/java/org/apache/uniffle/coordinator/CoordinatorServer.java

@@ -120,6 +120,9 @@ public void stopServer() throws Exception {
     if (jettyServer != null) {
       jettyServer.stop();
     }
+    if (applicationManager != null) {
+      applicationManager.close();
+    }
     if (clusterManager != null) {
       clusterManager.close();
     }