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

Change-Id: I163ef20e11b65d19d68585ec075fd3cd224a573b
diff --git a/tests/daemon/face/unix-stream-channel.t.cpp b/tests/daemon/face/unix-stream-channel.t.cpp
index dcd0270..1a356c0 100644
--- a/tests/daemon/face/unix-stream-channel.t.cpp
+++ b/tests/daemon/face/unix-stream-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,
@@ -31,6 +31,7 @@
 #include <fstream>
 
 namespace nfd {
+namespace face {
 namespace tests {
 
 namespace fs = boost::filesystem;
@@ -44,7 +45,7 @@
     listenerEp = unix_stream::Endpoint("nfd-test-unix-stream-channel.sock");
   }
 
-  virtual unique_ptr<UnixStreamChannel>
+  unique_ptr<UnixStreamChannel>
   makeChannel() final
   {
     return make_unique<UnixStreamChannel>(listenerEp);
@@ -174,4 +175,5 @@
 BOOST_AUTO_TEST_SUITE_END() // Face
 
 } // namespace tests
+} // namespace face
 } // namespace nfd