Simplify NO_KTLS path in SSL_sendfile.

Simplify NO_KTLS path in SSL_sendfile.

Avoid tripping over errno values from previous system calls in the
thread and just hardcode the specific error.  BIO_get_ktls_send()
should never be true in the NO_KTLS path, so the #ifdef could be
moved even higher up to assume that error path in the NO_KTLS case
instead.

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/10045)