Fix ossl_statem_client_max_message_size() for DTLS1_BAD_VER

The Change Cipher Spec message in this ancient pre-standard version of DTLS
that Cisco are unfortunately still using in their products, is 3 bytes.

Allow it.

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>

ssl/statem/statem_clnt.c

@@ -589,6 +589,8 @@ unsigned long ossl_statem_client_max_message_size(SSL *s)
             return SERVER_HELLO_DONE_MAX_LENGTH;
 
         case TLS_ST_CR_CHANGE:
+            if (s->version == DTLS1_BAD_VER)
+                return 3;
             return CCS_MAX_LENGTH;
 
         case TLS_ST_CR_SESSION_TICKET: