Currently NodeAgent on VM is able to send CSR request and store the key/cert on local disk.

NodeAgent on k8s is able to:

• Gets workload registration notification from flex volume driver.
• Use gRPC over unix domain socket to

We should merge these two so that it's able to send CSR on k8s and also temporarily writes cert into files, so that we have a working version before envoy SDS is ready. @wattli