TEST_NEGCACHE: Ensure root's uid and gid are always added to ncache
In order to do so two new functions have been introduced and
test_sss_ncache_prepopulate() has been modified in order to ensure that
root's uid and gid are always added to the negative cache.
Related: https://pagure.io/SSSD/sssd/issue/3460
Signed-off-by: Fabiano FidĂȘncio <fidencio@redhat.com>
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>