Show private subgroups if member of parent group

Merged Toon Claes requested to merge tc-fix-group-finder-subgrouping into master

What does this MR do?

If the user is member of one of the parent groups, also private groups should be shown.

Why was this MR needed?

regression introduced by .

It uses the changes in gitlab-org/gitlab-ce!10885.

Does this MR meet the acceptance criteria?

What are the relevant issue numbers?

Closed gitlab-org/gitlab-ce#32135

Implementation for %9.3, because gitlab-org/gitlab-ce!11773 takes care of %9.2 .

Edited by Toon Claes