Use configured datacenter name

To allow datacenters to be in folders

Signed-off-by: Adam Stegman <astegman@pivotallabs.com>
Initial test for vsphere cpi attach disk

Signed-off-by: Adam Stegman <astegman@pivotallabs.com>
Add tests for vsphere datacenter folders

Signed-off-by: Adam Stegman <astegman@pivotallabs.com>
Do not check the disk path after it was checked

Signed-off-by: Adam Stegman <astegman@pivotallabs.com>
Refactor vsphere cpi

Split out upload file and fetch file to FileProvider.
Aplit out agent environment reader setter to AgentEnv.
Add tests.

Signed-off-by: Adam Stegman <astegman@pivotallabs.com>