auth_get_canonical_hostname in portable code.

"refactor canohost.c" replaced get_canonical_hostname, this makes the
same change to some portable-specific code.
diff --git a/auth.c b/auth.c
index aae0593..55629b3 100644
--- a/auth.c
+++ b/auth.c
@@ -318,11 +318,12 @@
 	    strncmp(method, "keyboard-interactive", 20) == 0 ||
 	    strcmp(method, "challenge-response") == 0))
 		record_failed_login(authctxt->user,
-		    get_canonical_hostname(options.use_dns), "ssh");
+		    auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
 # ifdef WITH_AIXAUTHENTICATE
 	if (authenticated)
 		sys_auth_record_login(authctxt->user,
-		    get_canonical_hostname(options.use_dns), "ssh", &loginmsg);
+		    auth_get_canonical_hostname(ssh, options.use_dns), "ssh",
+		    &loginmsg);
 # endif
 #endif
 #ifdef SSH_AUDIT_EVENTS
@@ -653,7 +654,7 @@
 		    user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
 #ifdef CUSTOM_FAILED_LOGIN
 		record_failed_login(user,
-		    get_canonical_hostname(options.use_dns), "ssh");
+		    auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
 #endif
 #ifdef SSH_AUDIT_EVENTS
 		audit_event(SSH_INVALID_USER);