model: Finalizing implementation of FaceMetric::Status tracing

Adding test case (ndnSIM-fib-entry), which can be used as an example how
to set up tracing.
diff --git a/test/ndnSIM-tests.cc b/test/ndnSIM-tests.cc
index 3f0c319..688fca4 100644
--- a/test/ndnSIM-tests.cc
+++ b/test/ndnSIM-tests.cc
@@ -23,6 +23,7 @@
 
 #include "ndnSIM-serialization.h"
 #include "ndnSIM-pit.h"
+#include "ndnSIM-fib-entry.h"
 
 namespace ns3
 {
@@ -34,9 +35,10 @@
     : TestSuite ("ndnSIM-suite", UNIT)
   {
     SetDataDir (NS_TEST_SOURCEDIR);
-    
+
     AddTestCase (new InterestSerializationTest ());
     AddTestCase (new ContentObjectSerializationTest ());
+    AddTestCase (new FibEntryTest ());
     // AddTestCase (new PitTest ());
   }
 };