negcache: avoid "is_*_local" calls in some cases
"use_local_negative" argument of `sss_ncache_set_str()` function
only makes sense in case of non permanent record.
So it is possible to avoid blocking (and thus dangerous) "is_local*()"
calls in case "permanent == true"
Resolves: https://pagure.io/SSSD/sssd/issue/3963
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>