Compilation fixes after upgrade to NFD 0.6.6 and removal of old-style CS

Change-Id: I5472ae71675d8419d8d6c70990182ef028803087
diff --git a/examples/ndn-tree-cs-tracers.cpp b/examples/ndn-tree-cs-tracers.cpp
index cee7302..5cac62b 100644
--- a/examples/ndn-tree-cs-tracers.cpp
+++ b/examples/ndn-tree-cs-tracers.cpp
@@ -69,8 +69,8 @@
 
   // Install NDN stack on all nodes
   ndn::StackHelper ndnHelper;
-  ndnHelper.SetOldContentStore("ns3::ndn::cs::Lru", "MaxSize",
-                               "100"); // default ContentStore parameters
+  ndnHelper.setPolicy("nfd::cs::lru");
+  ndnHelper.setCsSize(100);
   ndnHelper.InstallAll();
 
   // Choosing forwarding strategy