Comment 5 for bug 1606177

Now Fuel API insists on adding of all available networks to nodes' interfaces.

https://github.com/openstack/fuel-web/blob/193f9aef7f7448536c828179b16bc27862218772/nailgun/nailgun/extensions/network_manager/validators/network.py#L937

It can be done via CLI now. But it's not always needed to have all the networks mapped on every node. So, it would be better to check presence on required network roles on nodes instead. Now, presence of required network roles on nodes is checked before deployment (it is done for network templates case but I'm not sure whether it is done for case w/o templates).

So, it's needed to change the rule to make setup more user-friendly from:

- all nodes must have all available networks assigned

to

- all nodes must have all required network roles assigned (different node roles require different sets of network roles).

To check network roles is slightly more complicated task as we need to walk through one more link: node -> interface -> network -> network role.

Probably, this check will be much slower than current validation. Then, it can be done not in NodeNICsHandler but during "Network Verification" procedure and before deployment (to not slow down networks-to-interfaces assignment).