Change namespace of DummyClientFace, Signal, Segmenter

refs #3940

Change-Id: I67ca0ecb8c916aab411a2f90454e0d25925978cd
diff --git a/tests/peek/ndnpeek.t.cpp b/tests/peek/ndnpeek.t.cpp
index 6e8869f..e7162b0 100644
--- a/tests/peek/ndnpeek.t.cpp
+++ b/tests/peek/ndnpeek.t.cpp
@@ -68,7 +68,7 @@
   }
 
 protected:
-  ndn::util::DummyClientFace face{m_io};
+  DummyClientFace face{m_io};
   output_test_stream output;
   unique_ptr<NdnPeek> peek;
 };