CLOUDSTACK-4296: fix a similar issue
(cherry picked from commit e2f47871d17351dae7555a48e0cd4d3dbe2ab2e2)
CLOUDSTACK-4266: UI > zone wizard > cluster step > make Nexus 1000v fields optional.
CLOUDSTACK-4266: UI > Infrastructure > clusters > create cluster dialog > make Nexus 1000v fields optional.