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/core/logger.cpp b/tests/core/logger.cpp
index 6694ece..0530dcc 100644
--- a/tests/core/logger.cpp
+++ b/tests/core/logger.cpp
@@ -10,12 +10,14 @@
 #include <boost/test/unit_test.hpp>
 #include <iostream>
 
+#include "tests/test-common.hpp"
 
 namespace nfd {
+namespace tests {
 
-BOOST_AUTO_TEST_SUITE(CoreLogger)
+BOOST_FIXTURE_TEST_SUITE(CoreLogger, BaseFixture)
 
-struct LoggerFixture
+struct LoggerFixture : protected BaseFixture
 {
   LoggerFixture()
     : m_savedBuf(std::cerr.rdbuf())
@@ -151,4 +153,5 @@
 
 BOOST_AUTO_TEST_SUITE_END()
 
+} // namespace tests
 } // namespace nfd