8132209: DiagnosticCommandImpl.getNotificationInfo() may expose internal representation

DiagnosticCommandImpl.getNotificationInfo() may expose internal representation

Reviewed-by: skoivu, fparain, jbachorik

jdk/src/jdk.management/share/classes/com/sun/management/internal/DiagnosticCommandImpl.java

@@ -343,7 +343,7 @@ public class DiagnosticCommandImpl extends NotificationEmitterSupport
                                                    "Diagnostic Framework Notification");
             }
         }
-        return notifInfo;
+        return notifInfo.clone();
     }
 
     private static long seqNumber = 0;