face: move Channel and subclasses into nfd::face namespace

Change-Id: I163ef20e11b65d19d68585ec075fd3cd224a573b
diff --git a/tests/daemon/face/tcp-channel.t.cpp b/tests/daemon/face/tcp-channel.t.cpp
index 6b7dc36..8068364 100644
--- a/tests/daemon/face/tcp-channel.t.cpp
+++ b/tests/daemon/face/tcp-channel.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2014-2016,  Regents of the University of California,
+ * Copyright (c) 2014-2017,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -30,6 +30,7 @@
 #include <boost/mpl/vector.hpp>
 
 namespace nfd {
+namespace face {
 namespace tests {
 
 BOOST_AUTO_TEST_SUITE(Face)
@@ -64,4 +65,5 @@
 BOOST_AUTO_TEST_SUITE_END() // Face
 
 } // namespace tests
+} // namespace face
 } // namespace nfd