Add test for missing CertificateStatus message

If the client sends a status_request extension in the ClientHello
and the server responds with a status_request extension in the
ServerHello then normally the server will also later send a
CertificateStatus message. However this message is *optional* even
if the extensions were sent. This adds a test to ensure that if
the extensions are sent then we can still omit the message.

Reviewed-by: Viktor Dukhovni <viktor@openssl.org>

util/TLSProxy/ClientHello.pm

@@ -58,6 +58,7 @@ package TLSProxy::ClientHello;
 use parent 'TLSProxy::Message';
 
 use constant {
+    EXT_STATUS_REQUEST => 5,
     EXT_ENCRYPT_THEN_MAC => 22,
     EXT_EXTENDED_MASTER_SECRET => 23,
     EXT_SESSION_TICKET => 35