Fix accidental KDC use of replay cache

r24464 (ticket #6804) intended to remove the KDC replay cache by
eliminating all of the USE_RCACHE code, but it had the unintended side
effect of causing krb5_rd_req_decoded to use the default server
rcache.  Using this cache is much less efficient because it is opened
and re-read for each request.

Set appropriate flags on the auth context to disable replay cache use
for TGS requests altogether.

ticket: 6941
target_version: 1.9.2
tags: pullup

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@25076 dc483132-0cff-0310-8789-dd5450dbe970

src/kdc/kdc_util.c

@@ -245,6 +245,10 @@ kdc_process_tgs_req(krb5_kdc_req *request, const krb5_fulladdr *from,
     if ((retval = krb5_auth_con_init(kdc_context, &auth_context)))
         goto cleanup;
 
+    /* Don't use a replay cache. */
+    if ((retval = krb5_auth_con_setflags(kdc_context, auth_context, 0)))
+        goto cleanup;
+
     if ((retval = krb5_auth_con_setaddrs(kdc_context, auth_context, NULL,
                                          from->address)) )
         goto cleanup_auth_context;