security: use exponential backoff in CertificateFetcherFromNetwork

refs: #4718, #4712

Change-Id: I8def533528b82ea00096e9d87897acf31dff24a4
diff --git a/src/security/v2/certificate-bundle-fetcher.cpp b/src/security/v2/certificate-bundle-fetcher.cpp
index 227a434..9375aa4 100644
--- a/src/security/v2/certificate-bundle-fetcher.cpp
+++ b/src/security/v2/certificate-bundle-fetcher.cpp
@@ -175,7 +175,7 @@
       m_certStorage->cacheUnverifiedCert(Certificate(block));
     }
 
-    auto cert = m_certStorage->getUnverifiedCertCache().find(certRequest->m_interest);
+    auto cert = m_certStorage->getUnverifiedCertCache().find(certRequest->interest);
     continueValidation(*cert, state);
   }
 }