This patch implements the multi-vif of VIF-Handler And Vif
Drivers Design.
This patch creates a new driver type MultiVIFDriver. It will
be the base class of real drivers like sriov,
additional_subnet and npwg_multiple_interfaces. Each of the
derived driver should implement the parsing of the additional
interfaces definition in K8S pods, and call VIF driver to
either create or acquire the Neutron port and its VIF object.
A list of enabled drivers can be returned by its class method.
So that the VIFHandler can invoke each driver one by one to
get the whole list of interfaces for one pod.
Partially Implements: blueprint multi-vif-pods
Change-Id: I8b5175a4637b18a0b574e27674a217865afb22b7
Signed-off-by: Peng Liu <pliu@redhat.com>
aaeb4f4687