rebaes to the new master branch from named-data/ndncert

Change-Id: I4d40daa5d1047a02fe814c464c73f06666c73bc7
diff --git a/src/challenge-module/challenge-credential.cpp b/src/challenge-module/challenge-credential.cpp
index 16724bc..bdc8b37 100644
--- a/src/challenge-module/challenge-credential.cpp
+++ b/src/challenge-module/challenge-credential.cpp
@@ -112,7 +112,7 @@
   ss2.clear();
 
   // verify the credential and the self-signed cert
-  Name signingKeyName = cert->getSignatureInfo().getKeyLocator().getName();
+  Name signingKeyName = cert->getSignature().getKeyLocator().getName();
   for (auto anchor : m_trustAnchors) {
     if (anchor.getKeyName() == signingKeyName) {
       if (security::verifySignature(*cert, anchor) && security::verifySignature(*self, *cert)