Remove legacy network model in tests and compute manager

Update unit tests to use current network info model, remove
old legacy "network, mapping" model. This patch also removes
code for compatible with Folsom vif db info cache in compute
manager.

Partly implement blueprint nova-network-legacy

Change-Id: I3c18d786fb3eb7105be89ccac96c6fd3d078853d
Merge "Remove legacy network model in tests and compute manager"