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

src/backend/libpq/auth.c

@@ -645,6 +645,22 @@ ClientAuthentication(Port *port)
 #endif
 	}
 
+	if (Log_connections && status == STATUS_OK &&
+		!MyClientConnectionInfo.authn_id)
+	{
+		/*
+		 * Normally, if log_connections is set, the call to set_authn_id()
+		 * will log the connection.  However, if that function is never
+		 * called, perhaps because the trust method is in use, then we handle
+		 * the logging here instead.
+		 */
+		ereport(LOG,
+				errmsg("connection authenticated: user=\"%s\" method=%s "
+					   "(%s:%d)",
+					   port->user_name, hba_authname(port->hba->auth_method),
+					   port->hba->sourcefile, port->hba->linenumber));
+	}
+
 	if (ClientAuthentication_hook)
 		(*ClientAuthentication_hook) (port, status);