Stop client from sending Certificate message when not requested

In a non client-auth renegotiation where the original handshake *was*
client auth, then the client will send a Certificate message anyway
resulting in a connection failure.

Fixes #1920

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1982)

ssl/statem/statem.c

@@ -355,6 +355,7 @@ static int state_machine(SSL *s, int server)
             s->hit = 0;
 
             s->s3->tmp.cert_request = 0;
+            s->s3->tmp.cert_req = 0;
 
             if (SSL_IS_DTLS(s)) {
                 st->use_timer = 1;