face: refactor NullFace as LinkService+Transport

refs #3278

Change-Id: I424f70f9402823d58d097671bab8c0c2dc4f2d3b
diff --git a/daemon/nfd.cpp b/daemon/nfd.cpp
index 2676a3a..bcc5926 100644
--- a/daemon/nfd.cpp
+++ b/daemon/nfd.cpp
@@ -90,9 +90,9 @@
 
   initializeManagement();
 
-  m_forwarder->getFaceTable().addReserved(make_shared<NullFace>(), FACEID_NULL);
-  m_forwarder->getFaceTable().addReserved(make_shared<NullFace>(FaceUri("contentstore://")),
-                                          FACEID_CONTENT_STORE);
+  FaceTable& faceTable = m_forwarder->getFaceTable();
+  faceTable.addReserved(face::makeNullFace(), FACEID_NULL);
+  faceTable.addReserved(face::makeNullFace(FaceUri("contentstore://")), FACEID_CONTENT_STORE);
 
   PrivilegeHelper::drop();