HADOOP-14230. TestAdlFileSystemContractLive fails to clean up. Contributed by John Zhuge.

(cherry picked from commit d1b7439b48caa18d64a94be1ad5e4927ce573ab8)

hadoop-tools/hadoop-azure-datalake/src/test/java/org/apache/hadoop/fs/adl/live/TestAdlFileSystemContractLive.java

@@ -45,9 +45,8 @@ public class TestAdlFileSystemContractLive extends FileSystemContractBaseTest {
   protected void tearDown() throws Exception {
     if (AdlStorageConfiguration.isContractTestEnabled()) {
       cleanup();
-      adlStore = null;
-      fs = null;
     }
+    super.tearDown();
   }
 
   private void cleanup() throws IOException {