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/table/pit.cpp b/tests/table/pit.cpp
index 916db81..f366ea2 100644
--- a/tests/table/pit.cpp
+++ b/tests/table/pit.cpp
@@ -5,13 +5,14 @@
  */
 
 #include "table/pit.hpp"
-#include "../face/dummy-face.hpp"
+#include "tests/face/dummy-face.hpp"
 
-#include <boost/test/unit_test.hpp>
+#include "tests/test-common.hpp"
 
 namespace nfd {
+namespace tests {
 
-BOOST_AUTO_TEST_SUITE(TablePit)
+BOOST_FIXTURE_TEST_SUITE(TablePit, BaseFixture)
 
 BOOST_AUTO_TEST_CASE(EntryInOutRecords)
 {
@@ -288,4 +289,5 @@
 
 BOOST_AUTO_TEST_SUITE_END()
 
+} // namespace tests
 } // namespace nfd