tests: respect naming conventions and improve nesting of some test suites

Change-Id: I255c27b552b32570871a9d5f8bda814ba8723c80
Refs: #2497
diff --git a/tests/unit-tests/security/pib-data-fixture.hpp b/tests/unit-tests/security/pib-data-fixture.hpp
index 04db21d..5e92dd1 100644
--- a/tests/unit-tests/security/pib-data-fixture.hpp
+++ b/tests/unit-tests/security/pib-data-fixture.hpp
@@ -19,8 +19,8 @@
  * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
  */
 
-#ifndef NDN_TESTS_PIB_DATA_FIXTURE_HPP
-#define NDN_TESTS_PIB_DATA_FIXTURE_HPP
+#ifndef NDN_TESTS_SECURITY_PIB_DATA_FIXTURE_HPP
+#define NDN_TESTS_SECURITY_PIB_DATA_FIXTURE_HPP
 
 #include "security/v1/identity-certificate.hpp"
 
@@ -61,4 +61,4 @@
 } // namespace security
 } // namespace ndn
 
-#endif // NDN_TESTS_PIB_DATA_FIXTURE_HPP
+#endif // NDN_TESTS_SECURITY_PIB_DATA_FIXTURE_HPP