fix verify signature bug;
add log info when content cannot be verified in fetcher

Change-Id: I7742f46848a3e108e8f57b2e8c39d044e6eb4997
diff --git a/ccnx/ccnx-wrapper.cpp b/ccnx/ccnx-wrapper.cpp
index af64b87..c498515 100644
--- a/ccnx/ccnx-wrapper.cpp
+++ b/ccnx/ccnx-wrapper.cpp
@@ -669,7 +669,7 @@
 bool
 CcnxWrapper::verifyPco(PcoPtr &pco)
 {
-  bool verified = ccn_verify_content(m_handle, pco->msg(), (ccn_parsed_ContentObject *)pco->pco());
+  bool verified = (ccn_verify_content(m_handle, pco->msg(), (ccn_parsed_ContentObject *)pco->pco()) == 0);
   pco->setVerified(verified);
   return verified;
 }