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

Change-Id: I163ef20e11b65d19d68585ec075fd3cd224a573b
diff --git a/daemon/face/internal-transport.hpp b/daemon/face/internal-transport.hpp
index 78f62a2..6296110 100644
--- a/daemon/face/internal-transport.hpp
+++ b/daemon/face/internal-transport.hpp
@@ -50,7 +50,7 @@
 
 /** \brief implements a forwarder-side transport that can be paired with another
  */
-class InternalForwarderTransport : public face::Transport, public InternalTransportBase
+class InternalForwarderTransport : public Transport, public InternalTransportBase
 {
 public:
   InternalForwarderTransport(const FaceUri& localUri = FaceUri("internal://"),