Add unit test in vsphere cpi for methods attach_independent_disk, detach_independent_disk, set_vmdk_content, attach_disk, detach_disk and configure_networks
Add system_vmdk_template stage in stemcell builder
Update bosh_agent to use vmdk template workflow to load settings
Update vsphere cpi to use vmdk template workflow
Add 'srm' flag in bat deployment manifest
 Update vsphere cpi lifecycle test to read configuration from environment variables
Remove system_vdiskmanager stage for vsphere
temperorily remove dns setting update