Comment 8 for bug 1428434

> Actually I think the port will be assigned to some random subnet

I have discussed it with one guy from neutron core team. He said, that in current case this port will be created in all subnets, which assigned on network. So it's valid case (honestly I though that it does not work at all :) ) and it's nrcessary to add some validation for it.

> Maybe the best we can do here is add documentation to the port network
property to encourage users to specify fixed_ip.subnet instead if known.

I agree, we should show the right way how to use it.