Initialize NodeStatus with current network interface data by default

[daniil-berg]

Instead of calling NetworkInterfaces.update_node_status from the get_status method of the storage/distributor file controller, we can add a pre-root-validator to the NodeStatus model class that gets the NetworkInterface instance and provides default values for the status object from that network interface. This would simplify the get_status methods considerably and make the update_node_status method obsolete.