CACHE_REQ: Don't error out when searching by id = 0
This code path can be easily triggered by calling `id 0` and SSSD should
not error out in this case.
Previous patches in this series already add uid and gid 0 to the
negative cache and we can properly handle this situation.
Related: https://pagure.io/SSSD/sssd/issue/3460
Signed-off-by: Fabiano FidĂȘncio <fidencio@redhat.com>
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>