Fix LDAP group sync for nested groups

Merged Michael Kozono requested to merge mk-fix-issue-3854 into master

What does this MR do?

Fixes LDAP group sync for nested groups.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

What are the relevant issue numbers?

Fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/3854

Edited by Michael Kozono