Don't treat PACKET_remaining() as boolean

Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3244)

ssl/statem/statem_clnt.c

@@ -1714,7 +1714,7 @@ MSG_PROCESS_RETURN tls_process_server_certificate(SSL *s, PACKET *pkt)
                                         &al, NULL, chainidx == 0)
                 || !tls_parse_all_extensions(s, SSL_EXT_TLS1_3_CERTIFICATE,
                                              rawexts, x, chainidx, &al,
-                                                 !PACKET_remaining(pkt))) {
+                                             PACKET_remaining(pkt) == 0)) {
                 OPENSSL_free(rawexts);
                 goto f_err;
             }

ssl/statem/statem_srvr.c

@@ -3220,7 +3220,7 @@ MSG_PROCESS_RETURN tls_process_client_certificate(SSL *s, PACKET *pkt)
                                         &al, NULL, chainidx == 0)
                 || !tls_parse_all_extensions(s, SSL_EXT_TLS1_3_CERTIFICATE,
                                              rawexts, x, chainidx, &al,
-                                                 !PACKET_remaining(&spkt))) {
+                                             PACKET_remaining(&spkt) == 0)) {
                 OPENSSL_free(rawexts);
                 goto f_err;
             }