VMware: Ensure Neutron networking works with VMware drivers

Fixes bug 1202042

A new utility method, is_neutron, is added. This returns True
if Neutron/Quantum is used by the network_api_class.

Change-Id: Id1d1f29a02e906b98853670ea2ad589f04eba595
Merge "VMware: Ensure Neutron networking works with VMware drivers"