In some more complex clouds there can not only be more than one valid network
on a server that NAT can attach to, there can also be more than one valid
network from which to get a NAT address. Allow flagging a network so that it
can be found.
Change-Id: I3d8dd6d734a1013d2d4a43e11c3538c3a345820b
6d8633f5dd