HDFS-16852. Skip KeyProviderCache shutdown hook registration if already shutting down (#5160)

Signed-off-by: Erik Krogen <xkrogen@apache.org>

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/KeyProviderCache.java

@@ -68,8 +68,11 @@ public class KeyProviderCache {
         })
         .build();
 
-    ShutdownHookManager.get().addShutdownHook(new KeyProviderCacheFinalizer(),
-        SHUTDOWN_HOOK_PRIORITY);
+    // Register the shutdown hook when not in shutdown
+    if (!ShutdownHookManager.get().isShutdownInProgress()) {
+      ShutdownHookManager.get().addShutdownHook(
+          new KeyProviderCacheFinalizer(), SHUTDOWN_HOOK_PRIORITY);
+    }
   }
 
   public KeyProvider get(final Configuration conf,