Don't acknowledge a servername following warning alert in servername cb
If the servername cb decides to send back a warning alert then the
handshake continues, but we should not signal to the client that the
servername has been accepted.
@@ -1009,6 +1009,7 @@ static int final_server_name(SSL *s, unsigned int context, int sent)
/* TLSv1.3 doesn't have warning alerts so we suppress this */
if (!SSL_IS_TLS13(s))
ssl3_send_alert(s, SSL3_AL_WARNING, altmp);
+ s->servername_done = 0;
return 1;
case SSL_TLSEXT_ERR_NOACK:
