BUG/MEDIUM: ssl: Fix handling of TLS 1.3 KeyUpdate messages

BUG/MEDIUM: ssl: Fix handling of TLS 1.3 KeyUpdate messages

In OpenSSL 1.1.1 TLS 1.3 KeyUpdate messages will trigger the callback
that is used to verify renegotiation is disabled. This means that these
KeyUpdate messages fail. In OpenSSL 1.1.1 a better mechanism is
available with the SSL_OP_NO_RENEGOTIATION flag that disables any TLS
1.2 and earlier negotiation.

So if this SSL_OP_NO_RENEGOTIATION flag is available, instead of having
a manual check, trust OpenSSL and disable the check. This means that TLS
1.3 KeyUpdate messages will work properly.

Reported-By: Adam Langley <agl@imperialviolet.org>