face: introduce NullTransport and use it in several places

Refs: #4528
Change-Id: Icc7a77232bca1a700ce1319493c15a85d05d7488
diff --git a/daemon/face/null-face.cpp b/daemon/face/null-face.cpp
index 2ce5c98..77178c6 100644
--- a/daemon/face/null-face.cpp
+++ b/daemon/face/null-face.cpp
@@ -25,7 +25,7 @@
 
 #include "null-face.hpp"
 #include "null-link-service.hpp"
-#include "internal-transport.hpp"
+#include "null-transport.hpp"
 
 namespace nfd {
 namespace face {
@@ -36,7 +36,7 @@
   // FIB could restrict creating a nexthop record toward a non-local face in /localhost namespace.
   // Therefore, NullFace has scope=local to enable creating a "blackhole" FIB entry under /localhost.
   return make_shared<Face>(make_unique<NullLinkService>(),
-                           make_unique<InternalForwarderTransport>(uri, uri, ndn::nfd::FACE_SCOPE_LOCAL));
+                           make_unique<NullTransport>(uri, uri, ndn::nfd::FACE_SCOPE_LOCAL));
 }
 
 } // namespace face