Comment 4 for bug 1402844

>it is nova-network and I pass this propety?
Sahara will return validation error

>it is neutron with multiple networks and I do not pass this property?
Sahara will return validation error

So, neutron_management_network must be provided in case (and only in case) of neutron. It should be provided either in cluster template or in cluster (or in both, value from cluster will be used in this case).