We were returning '' for the first entry when hostcat and usercat were
set to all. All subsequent entries were padded with - which effectively
denied access.
This requires slapi-nis 0.40+
https://fedorahosted.org/freeipa/ticket/2192
We originally designed netgroups to use a special membership attribute,
memberNisNetgroup. We changed it at implementation time but never updated
the mapping.
https://fedorahosted.org/freeipa/ticket/2359