security: change enum to enum class in security-common.hpp

Change-Id: I5565c845cd57f3457c8120b11399a105fa83418d
Refs: #3083
diff --git a/tests/unit-tests/security/dummy-keychain.cpp b/tests/unit-tests/security/dummy-keychain.cpp
index c7e7a10..27eccb2 100644
--- a/tests/unit-tests/security/dummy-keychain.cpp
+++ b/tests/unit-tests/security/dummy-keychain.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2013-2015 Regents of the University of California.
+ * Copyright (c) 2013-2016 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -127,7 +127,7 @@
 KeyType
 DummyPublicInfo::getPublicKeyType(const Name& keyName)
 {
-  return KEY_TYPE_RSA;
+  return KeyType::RSA;
 }
 
 bool