poke: exit with status 5 if prefix registration fails

Change-Id: I2147570c37146011c9a4e8c024b74bcafdf18e4e
diff --git a/tools/peek/ndnpeek/main.cpp b/tools/peek/ndnpeek/main.cpp
index f763b96..ead3d70 100644
--- a/tools/peek/ndnpeek/main.cpp
+++ b/tools/peek/ndnpeek/main.cpp
@@ -150,7 +150,7 @@
     program.start();
     face.processEvents();
 
-    return static_cast<int>(program.getResultCode());
+    return static_cast<int>(program.getResult());
   }
   catch (const std::exception& e) {
     std::cerr << "ERROR: " << e.what() << std::endl;