Refactor and modernize namespace declarations

Move all unit tests to namespace nfd::tests

Delete unused header core/algorithm.hpp

Change-Id: I5591f0c5f3bb5db67f8b45fae95471f8a555ca68
diff --git a/tests/daemon/rib/rib-update.t.cpp b/tests/daemon/rib/rib-update.t.cpp
index 90c80f0..533439a 100644
--- a/tests/daemon/rib/rib-update.t.cpp
+++ b/tests/daemon/rib/rib-update.t.cpp
@@ -29,9 +29,9 @@
 #include "tests/test-common.hpp"
 #include "tests/daemon/rib/create-route.hpp"
 
-namespace nfd {
-namespace rib {
-namespace tests {
+namespace nfd::tests {
+
+using namespace nfd::rib;
 
 BOOST_AUTO_TEST_SUITE(TestRibUpdate)
 
@@ -76,6 +76,4 @@
 
 BOOST_AUTO_TEST_SUITE_END() // TestRibUpdate
 
-} // namespace tests
-} // namespace rib
-} // namespace nfd
+} // namespace nfd::tests