Fix inconsistent check of UNSAFE_LEGACY_RENEGOTIATION

The check for SSL3_FLAGS_ALLOW_UNSAFE_LEGACY_RENEGOTIATION is
inconsistent. Most places check SSL->options, one place is checking
SSL_CTX->options; fix that.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Kurt Roeckx <kurt@roeckx.be>
GH: #3523
(cherry picked from commit dffdcc77)