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

Change-Id: I163ef20e11b65d19d68585ec075fd3cd224a573b
diff --git a/tests/daemon/face/tcp-channel-fixture.hpp b/tests/daemon/face/tcp-channel-fixture.hpp
index 869a76c..4f63035 100644
--- a/tests/daemon/face/tcp-channel-fixture.hpp
+++ b/tests/daemon/face/tcp-channel-fixture.hpp
@@ -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,
@@ -31,12 +31,13 @@
 #include "channel-fixture.hpp"
 
 namespace nfd {
+namespace face {
 namespace tests {
 
 class TcpChannelFixture : public ChannelFixture<TcpChannel, tcp::Endpoint>
 {
 protected:
-  virtual unique_ptr<TcpChannel>
+  unique_ptr<TcpChannel>
   makeChannel(const boost::asio::ip::address& addr, uint16_t port = 0) final
   {
     if (port == 0)
@@ -45,7 +46,7 @@
     return make_unique<TcpChannel>(tcp::Endpoint(addr, port));
   }
 
-  virtual void
+  void
   connect(TcpChannel& channel) final
   {
     g_io.post([&] {
@@ -65,6 +66,7 @@
 };
 
 } // namespace tests
+} // namespace face
 } // namespace nfd
 
 #endif // NFD_TESTS_DAEMON_FACE_TCP_CHANNEL_FIXTURE_HPP