Revert "HADOOP-16344. Make DurationInfo public unstable."

This reverts commit 829848b.

Change-Id: Ied91250e191b2ba701a8fc697c78b3756ce76be8

Author: steveloughran

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/DurationInfo.java

@@ -29,8 +29,8 @@
  * This allows it to be used in a try-with-resources clause, and have the
  * duration automatically logged.
  */
-@Public
-@Unstable
+@InterfaceAudience.Private
+@InterfaceStability.Unstable
 public class DurationInfo extends OperationDuration
     implements AutoCloseable {
   private final String text;