rib: Refactor initialization of NRD instance

This commit also makes Face used inside NRD be adaptive to nfd.conf.
More specifically, it will use the same unix socket path as specified in
face_system.unix section.  If this section is not present, it will use
the same tcp port as specified in face_system.tcp section.  If tcp
section is also absent, nrd will abort execution.

Change-Id: I48f75ddf972f259055cd61824e3c228ca1d6a639
Refs: #2496
diff --git a/daemon/main.cpp b/daemon/main.cpp
index aa2d822..eaa4e26 100644
--- a/daemon/main.cpp
+++ b/daemon/main.cpp
@@ -41,7 +41,7 @@
 
 NFD_LOG_INIT("NFD");
 
-class NfdRunner
+class NfdRunner : noncopyable
 {
 public:
   explicit