This makes conn.logs a bit prettier (and smaller) because all lines that
do not use a tunnel will now have a "-" instead of the "(empty)" for
tunnel_parents.
In the *service* field of connection records, GridFTP control channels
are labeled as "gridftp" and data channels as "gridftp-data".
Added *client_subject* and *client_issuer_subject* as &log'd fields to
SSL::Info record. Also added *client_cert* and *client_cert_chain*
fields to track client cert chain.