Generate new LOG for "trust" connections under log_connections

Generate new LOG for "trust" connections under log_connections

Adding an extra LOG for connections that have not set an authn ID, like
when the "trust" authentication method is used, is useful for audit
purposes.

A couple of TAP tests for SSL and authentication need to be tweaked to
adapt to this new LOG generated, as some scenarios expected no logs but
they now get a hit.

Reported-by: Shaun Thomas
Author: Jacob Champion
Reviewed-by: Robert Haas, Michael Paquier
Discussion: https://postgr.es/m/CAFdbL1N7-GF-ZXKaB3XuGA+CkSmnjFvqb8hgjMnDfd+uhL2u-A@mail.gmail.com