**breaking change**: Switch Face and related classes to v2::KeyChain

security::v2::KeyChain is now exposed as ndn::KeyChain, which should
ensure that dependent code can be mostly compiled.  However, expect code
that explicitly uses the old KeyChain interface to be broken.

Change-Id: I7330d0250d92f3f0f2570ab6d0214ab3dfdd18cc
Refs: #3098
diff --git a/tests/unit-tests/security/v2/key-chain.t.cpp b/tests/unit-tests/security/v2/key-chain.t.cpp
index 4eaf75e..d1a954c 100644
--- a/tests/unit-tests/security/v2/key-chain.t.cpp
+++ b/tests/unit-tests/security/v2/key-chain.t.cpp
@@ -47,6 +47,12 @@
     unsetenv("NDN_CLIENT_PIB");
     unsetenv("NDN_CLIENT_TPM");
   }
+
+  ~TestHomeAndPibFixture()
+  {
+    const_cast<std::string&>(KeyChain::getDefaultPibLocator()).clear();
+    const_cast<std::string&>(KeyChain::getDefaultTpmLocator()).clear();
+  }
 };
 
 struct PibPathConfigFileHome