tests: resetGlobalIoService for every test

All tests must use BaseFixture or a fixture derived from it to get this feature.

This commit also fixes a few warnings in tests/mgmt, and moves test cases into nfd::tests namespace.

refs #1290

Change-Id: I891441a5abce170e35648d463f7157b18429f79f
diff --git a/tests/face/dummy-face.hpp b/tests/face/dummy-face.hpp
index 45a3d43..969053a 100644
--- a/tests/face/dummy-face.hpp
+++ b/tests/face/dummy-face.hpp
@@ -11,6 +11,7 @@
 #include "face/local-face.hpp"
 
 namespace nfd {
+namespace tests {
 
 /** \class DummyFace
  *  \brief a Face for unit testing
@@ -50,11 +51,7 @@
     this->onReceiveData(data);
   }
 
-protected:
-  virtual void
-  afterSend()
-  {
-  }
+  EventEmitter<> afterSend;
 
 public:
   std::vector<Interest> m_sentInterests;
@@ -64,6 +61,7 @@
 typedef DummyFaceImpl<Face> DummyFace;
 typedef DummyFaceImpl<LocalFace> DummyLocalFace;
 
+} // namespace tests
 } // namespace nfd
 
 #endif // TEST_FACE_DUMMY_FACE_HPP