ping: set CanBePrefix=false

This commit also sets CanBePrefix in ndndump and ndnpoke tests.

refs #4581

Change-Id: Ie91839426acc02f1879495312ad7ef131e8dac57
diff --git a/tools/ping/README.md b/tools/ping/README.md
index 8c0c513..8df5adc 100644
--- a/tools/ping/README.md
+++ b/tools/ping/README.md
@@ -67,8 +67,10 @@
 one or more printable characters only, to make it easier for a human operator to read the logs.
 A client implementation MAY restrict this field to be non-empty and have printable characters only.
 
-The probe Interest SHOULD carry MustBeFresh selector by default.
-A client implementation MAY allow the operator to turn off MustBeFresh selector.
+The probe Interest SHOULD NOT carry CanBePrefix element.
+
+The probe Interest SHOULD carry MustBeFresh element.
+A client implementation MAY allow the operator to remove MustBeFresh element.
 
 ### Reply Data
 
diff --git a/tools/ping/client/ping.cpp b/tools/ping/client/ping.cpp
index c6290b0..7f2e2a4 100644
--- a/tools/ping/client/ping.cpp
+++ b/tools/ping/client/ping.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2014-2017,  Arizona Board of Regents.
+/*
+ * Copyright (c) 2014-2018,  Arizona Board of Regents.
  *
  * This file is part of ndn-tools (Named Data Networking Essential Tools).
  * See AUTHORS.md for complete list of ndn-tools authors and contributors.
@@ -62,6 +62,7 @@
   Name pingPacketName = makePingName(m_nextSeq);
 
   Interest interest(pingPacketName);
+  interest.setCanBePrefix(false);
   interest.setMustBeFresh(!m_options.shouldAllowStaleData);
   interest.setInterestLifetime(m_options.timeout);