Send a NewSessionTicket after using an external PSK

Treat a connection using an external PSK like we would a resumption and
send a single NewSessionTicket afterwards.

Fixes #6941
Reviewed-by: NViktor Dukhovni <viktor@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7097)

ssl/statem/extensions_srvr.c

@@ -1160,6 +1160,7 @@ int tls_parse_ctos_psk(SSL *s, PACKET *pkt, unsigned int context, X509 *x,
             ext = 1;
             if (id == 0)
                 s->ext.early_data_ok = 1;
+            s->ext.ticket_expected = 1;
         } else {
             uint32_t ticket_age = 0, now, agesec, agems;
             int ret;
@@ -1235,6 +1236,7 @@ int tls_parse_ctos_psk(SSL *s, PACKET *pkt, unsigned int context, X509 *x,
             SSL_SESSION_free(sess);
             sess = NULL;
             s->ext.early_data_ok = 0;
+            s->ext.ticket_expected = 0;
             continue;
         }
         break;