Enable network operations over neutron private nets

Enables communication between the savanna api server and the spawned
VMs over the specific network namespace associated with the selected
network.  The SSH and HTTP communication will be conducted over
netcat based subprocesses.  This feature is enabled when the
configuration indicates that neutron networking is enabled while
the use of public IPs is set to false.

Implements blueprint neutron-private-net-provisioning

Change-Id: I61d61a7ef6eccb04274549883dde489641d1da9b
Merge "Enable network operations over neutron private nets"