openssl s_server: print the accepting address and socket

The line saying ACCEPT is extended with a space followed by the the
address and port combination on which s_server accepts connections.
The address is written in such a way that s_client should be able to
accepts as argument for the '-connect' option.

Reviewed-by: Andy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5843)