Propose: VMware spawn refactor

A structured refactor of the vmwareapi spawn method to improve maintainability
of the vmware driver.

Goal: break up spawn method into reusable components

Phase 1: break out the nested inner methods to create components
Phase 2: consolidate vmware-specific image properties
Phase 3: create utilities for image manipulation steps

related to blueprint vmware-spawn-refactor

Change-Id: Iadeeb183b651fa424b31a3349338036c6c51858d
Merge "Propose: VMware spawn refactor"