Don't fail if the PSK identity doesn't match

In 1.1.0 s_server if the PSK identity doesn't match what we have then
a warning is printed and we continue the connection anyway. In 1.1.1,
if TLSv1.3 is used and the identity doesn't match then we abort the
connection. We should really be consistent with the old behaviour.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6659)