Improve get_node_networks in network manager

get_node_networks method from network manager
causes multiple queries to database on single api request

adding ip_addrs relationship allows to eagerload all required
data
viewonly required to prevent races in several fake tasks

Change-Id: I5f6fe92707b551b20c5140dd339b3e402a774ee7
Closes-Bug: #1328200
Merge "Improve get_node_networks in network manager"