Always duplicate the session on NewSessionTicket in TLSv1.3

Because NST messages arrive post-handshake, the session may have already
gone into the cache. Once in the cache a session must be immutable -
otherwise you could get multi-thread issues.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3008)