tests: fix build with clang-5.0

Change-Id: Id032651e3954dc124088e39a0bc84ec9a58aaeba
Refs: #4277
diff --git a/tests/unit-tests/security/v2/validator.t.cpp b/tests/unit-tests/security/v2/validator.t.cpp
index bb545e1..9945ef9 100644
--- a/tests/unit-tests/security/v2/validator.t.cpp
+++ b/tests/unit-tests/security/v2/validator.t.cpp
@@ -115,7 +115,7 @@
       face.receive(expiredCert);
     }
     else {
-      processInterest(interest);
+      originalProcessInterest(interest);
     }
   };