nss-idmap: add nss like calls with timeout and flags
This patch adds new calls to libsss_nss_idmap to get NSS like user and
group information directly from SSSD without using the system's NSS
interfaces.
Additionally a timeout and a flags options are added which are not
available for system's NSS.
Related to https://pagure.io/SSSD/sssd/issue/2478
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>