SDAP: Make nesting_level = 0 to ignore nested groups
Make ldap_group_nesting_level = 0 to ignore group nesting entirely.
Resolves:
https://fedorahosted.org/sssd/ticket/2294
Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
(cherry picked from commit c30f1d05d6c75080fbe8ea9868f291e7a331ad44)