ping: Tests for Ping and PingServer

This commit includes minor refactoring in Ping and PingServer to support unit testing

refs #2796

Change-Id: Id0172486aa07e129a90091d72594fbccbb5dbc06
diff --git a/tools/ping/server/ping-server.hpp b/tools/ping/server/ping-server.hpp
index c5e9634..242a54a 100644
--- a/tools/ping/server/ping-server.hpp
+++ b/tools/ping/server/ping-server.hpp
@@ -65,6 +65,12 @@
   run();
 
   /**
+   * @brief starts the Interest filter
+   */
+  void
+  start();
+
+  /**
    * @brief gets the number of pings received
    */
   int