AD: process non-posix nested groups using tokenGroups
When initgr is performed for AD supporting tokenGroups, do not skip
non-posix groups.
Resolves:
https://fedorahosted.org/sssd/ticket/2343
Reviewed-by: Michal Židek <mzidek@redhat.com>
(cherry picked from commit 4932db6258ccfb612a3a28eb6a618c2f042b9d58)