If we've sent a close_notify then we are restricted about what we can do
in response to handshake messages that we receive. However we can sensibly
process NewSessionTicket messages. We can also process a KeyUpdate message
as long as we also ignore any request for us to update our sending keys.
Reviewed-by: NTim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7114)