Man-in-the-middle attack with SessionTicketsDisabled in crypto/tls

When SessionTicketsDisabled is enabled, crypto/tls allowed man-in-the-middle attackers to spoof clients via unspecified vectors.

If the server enables TLS client authentication using certificates (this is rare) and explicitly sets SessionTicketsDisabled to true in the tls.Config, then a malicious client can falsely assert ownership of any client certificate it wishes.