The record version for ClientHello2 should be TLS1.2

According to TLSv1.3 draft-24 the record version for ClientHello2 should
be TLS1.2, and not TLS1.0 as it is now.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5377)