Integrate Azure-VNET CNI plugin to Kubernetes Windows nodes

[ofiliz]

Is this a request for help?:

No.

Is this an ISSUE or FEATURE REQUEST? (choose one):

Feature request.

What version of acs-engine?:

Applies to latest (v0.7)

Orchestrator and version (e.g. Kubernetes, DC/OS, Swarm)
Kubernetes, all versions.

What happened:
With Windows Server 2016 RS3 release, Windows now supports CNI plugins, so Kubernetes Windows nodes can take advantage of azure-vnet CNI plugins just like Kubernetes Linux nodes.

What you expected to happen:
We need to install and configure CNI on Kubernetes Windows nodes.

How to reproduce it (as minimally and precisely as possible):
N/A

Anything else we need to know:
Fix coming soon.