Improve and simplify code with modern C++ features

Change-Id: I28d84df3087492ab2ecbeb91169a2cde12c9e31e
diff --git a/tests/unit-tests/security/v2/trust-anchor-container.t.cpp b/tests/unit-tests/security/v2/trust-anchor-container.t.cpp
index 30749ac..efd6ca3 100644
--- a/tests/unit-tests/security/v2/trust-anchor-container.t.cpp
+++ b/tests/unit-tests/security/v2/trust-anchor-container.t.cpp
@@ -46,16 +46,15 @@
 public:
   AnchorContainerTestFixture()
   {
-    boost::filesystem::create_directory(boost::filesystem::path(UNIT_TEST_CONFIG_PATH));
+    namespace fs = boost::filesystem;
 
-    certDirPath = boost::filesystem::path(UNIT_TEST_CONFIG_PATH) / std::string("test-cert-dir");
-    boost::filesystem::create_directory(certDirPath);
+    fs::create_directory(fs::path(UNIT_TEST_CONFIG_PATH));
 
-    certPath1 = boost::filesystem::path(UNIT_TEST_CONFIG_PATH) /
-      std::string("test-cert-dir") / std::string("trust-anchor-1.cert");
+    certDirPath = fs::path(UNIT_TEST_CONFIG_PATH) / "test-cert-dir";
+    fs::create_directory(certDirPath);
 
-    certPath2 = boost::filesystem::path(UNIT_TEST_CONFIG_PATH) /
-      std::string("test-cert-dir") / std::string("trust-anchor-2.cert");
+    certPath1 = fs::path(UNIT_TEST_CONFIG_PATH) / "test-cert-dir" / "trust-anchor-1.cert";
+    certPath2 = fs::path(UNIT_TEST_CONFIG_PATH) / "test-cert-dir" / "trust-anchor-2.cert";
 
     identity1 = addIdentity("/TestAnchorContainer/First");
     cert1 = identity1.getDefaultKey().getDefaultCertificate();