Change SSL parameter SSL_session_reused const

This function only returns a status and does not modify the parameter.
Since similar function are already taking const parameters, also
change this function to have a const parameter.

Fixes #8934

CLA: trivial
Signed-off-by: Arne Schwabe <arne@rfc2549.org>

Reviewed-by: Kurt Roeckx <kurt@roeckx.be>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/8945)