HADOOP-13822. Use GlobalStorageStatistics.INSTANCE.reset() at FileSystem#clearStatistics(). Contribute by Brahma Reddy Battula

(cherry picked from commit aab9737a058c0bdeeb17c173e530b7e571315a56)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileSystem.java

@@ -3532,12 +3532,7 @@ public abstract class FileSystem extends Configured implements Closeable {
    * Reset all statistics for all file systems
    */
   public static synchronized void clearStatistics() {
-    final Iterator<StorageStatistics> iterator =
-        GlobalStorageStatistics.INSTANCE.iterator();
-    while (iterator.hasNext()) {
-      final StorageStatistics statistics = iterator.next();
-      statistics.reset();
-    }
+    GlobalStorageStatistics.INSTANCE.reset();
   }
 
   /**