Refactor and modernize namespace declarations

 * Completely remove inline namespace v2
 * Flatten some unnecessarily deep namespace nesting
 * Move DummyClientFace, Segmenter, SegmentFetcher to namespace ndn
 * Move all unit tests to namespace ndn::tests

Change-Id: I8bcfcf9fd669936a3277d2d5d505f765b4b05742
diff --git a/tests/unit/mgmt/dispatcher.t.cpp b/tests/unit/mgmt/dispatcher.t.cpp
index 9b01628..1e1c947 100644
--- a/tests/unit/mgmt/dispatcher.t.cpp
+++ b/tests/unit/mgmt/dispatcher.t.cpp
@@ -26,11 +26,9 @@
 #include "tests/test-common.hpp"
 #include "tests/unit/io-key-chain-fixture.hpp"
 
-namespace ndn {
-namespace mgmt {
-namespace tests {
+namespace ndn::tests {
 
-using namespace ndn::tests;
+using namespace ndn::mgmt;
 
 class DispatcherFixture : public IoKeyChainFixture
 {
@@ -43,7 +41,7 @@
   }
 
 public:
-  util::DummyClientFace face;
+  DummyClientFace face;
   mgmt::Dispatcher dispatcher;
   InMemoryStorageFifo& storage;
 };
@@ -473,6 +471,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestDispatcher
 BOOST_AUTO_TEST_SUITE_END() // Mgmt
 
-} // namespace tests
-} // namespace mgmt
-} // namespace ndn
+} // namespace ndn::tests