Modify is_tls13_capable() to take account of the servername cb
Modify is_tls13_capable() to take account of the servername cb

A servername cb may change the available certificates, so if we have one
set then we cannot rely on the configured certificates to determine if we
are capable of negotiating TLSv1.3 or not.

Fixes #13291

Reviewed-by: Tomas Mraz <973cc78d8b4cb00714230ba9be0225e917ab4ac6@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/13304)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl