Migrate get509() callsite to OpenSSLTransportCert

Summary:
Before removing `getX509()` from `AsyncTransportCertificate` we need to migrate
all the callsites to `OpenSSLTransportCertificate`.

Differential Revision: D30487611

fbshipit-source-id: 50deea4904b7b6a6c08c6d4fd0c635a4bc8774cb

folly/io/async/ssl/BasicTransportCertificate.h

@@ -33,7 +33,7 @@ class BasicTransportCertificate : public folly::OpenSSLTransportCertificate {
       return nullptr;
     }
     return std::make_unique<BasicTransportCertificate>(
-        cert->getIdentity(), cert->getX509());
+        cert->getIdentity(), OpenSSLTransportCertificate::tryExtractX509(cert));
   }
 
   BasicTransportCertificate(