kdc: Add ret to common svc req elements

We're logging SUCCESS even when the KDC sends error replies.  That's
because we're returning success to process_request() even when we send
errors to clients.  The error we want to send to the client, and that we
succeed or fail to send it, are different statuses.

Also, further move things into `r` and out of function arguments.

kdc/process.c

@@ -125,7 +125,7 @@ _kdc_audit_trail(kdc_request_t r, krb5_error_code ret)
 
     /* Get a symbolic name for some error codes */
 #define CASE(x)	case x : retname = #x; break
-    switch (ret) {
+    switch (ret ? ret : r->ret) {
     CASE(ENOMEM);
     CASE(EACCES);
     CASE(HDB_ERR_NOT_FOUND_HERE);