Ignore internal users on user counts

Merged James Lopez requested to merge fix/user-count-2 into master

What does this MR do?

Counts non-internal users only for active users filtering

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

I first went for creating a separate scope for this on https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1658 but then I changed my mind, since we may only want to show active non-internal.

Fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/2096