If a server has been configured to use an ECDSA certificate, we should
allow it regardless of whether the server's own supported groups list
includes the certificate's group.

Fixes #2033
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NBernd Edlinger <bernd.edlinger@hotmail.de>
(Merged from https://github.com/openssl/openssl/pull/5601)