vsphere-csi-driver: Incorrect repository layour for v2 Go Modules

Is this a BUG REPORT or FEATURE REQUEST?: /kind bug

What happened: Repository breaks the mandatory requirements of v2 Go Modules.

What you expected to happen: Fix go module requirements for semantic versioning

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

Anything else we need to know?:

• https://golang.org/cmd/go/#hdr-Module_compatibility_and_semantic_versioning
• https://blog.golang.org/v2-go-modules

Environment:

• csi-vsphere version: N/A
• vsphere-cloud-controller-manager version: N/A
• Kubernetes version: N/A
• vSphere version: N/A
• OS (e.g. from /etc/os-release): N/A
• Kernel (e.g. uname -a): N/A
• Install tools: N/A
• Others: N/A