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

Change-Id: I163ef20e11b65d19d68585ec075fd3cd224a573b
diff --git a/tests/daemon/face/channel-fixture.hpp b/tests/daemon/face/channel-fixture.hpp
index a8e619d..f764125 100644
--- a/tests/daemon/face/channel-fixture.hpp
+++ b/tests/daemon/face/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,
@@ -32,8 +32,11 @@
 #include <type_traits>
 
 namespace nfd {
+namespace face {
 namespace tests {
 
+using namespace nfd::tests;
+
 template<class ChannelT, class EndpointT>
 class ChannelFixture : public BaseFixture
 {
@@ -104,6 +107,7 @@
 };
 
 } // namespace tests
+} // namespace face
 } // namespace nfd
 
 #endif // NFD_TESTS_DAEMON_FACE_CHANNEL_FIXTURE_HPP