Disable nova-manage network commands with Neutron V2

When using nova-manage with neutron v2 API, all CRUD operations
should be done directly against the neutron API, rather than
using nova-manage.

Change-Id: I663bd06eb50872f16fc9889dde917277739fefce
Closes-Bug: #1019895
Merge "Disable nova-manage network commands with Neutron V2"