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

Change-Id: I5472ae71675d8419d8d6c70990182ef028803087
diff --git a/examples/ndn-congestion-topo-plugin.cpp b/examples/ndn-congestion-topo-plugin.cpp
index fa72462..427620b 100644
--- a/examples/ndn-congestion-topo-plugin.cpp
+++ b/examples/ndn-congestion-topo-plugin.cpp
@@ -57,7 +57,8 @@
 
   // Install NDN stack on all nodes
   ndn::StackHelper ndnHelper;
-  ndnHelper.SetOldContentStore("ns3::ndn::cs::Lru", "MaxSize", "10000");
+  ndnHelper.setPolicy("nfd::cs::lru");
+  ndnHelper.setCsSize(10000);
   ndnHelper.InstallAll();
 
   // Choosing forwarding strategy