remove using std

Change-Id: I268a92200a397f4fba0458f951f0a10b25ac0836
diff --git a/src/ca-storage/ca-storage.hpp b/src/ca-storage/ca-storage.hpp
index 99af926..e18a5bc 100644
--- a/src/ca-storage/ca-storage.hpp
+++ b/src/ca-storage/ca-storage.hpp
@@ -61,7 +61,7 @@
     CaStorageFactory& factory = getFactory();
     BOOST_ASSERT(factory.count(caStorageType) == 0);
     factory[caStorageType] = [] (const Name& caName, const std::string& path) {
-      return make_unique<CaStorageType>(caName, path);
+      return std::make_unique<CaStorageType>(caName, path);
     };
   }