Add a missing config value for Compute Nodes

Includes the linuxnet_interface_driver config parameter when
Neutron is enabled in Computes Nodes

Closes-Bug: #1251096
Change-Id: Ib1871970b6feb74364d77099999c4403190417d8
(cherry picked from commit 9e6486112777887e8b02e7d55fc342f27cb021ef)
Merge "Add a missing config value for Compute Nodes" into stable/havana