VCH Management APIs: Ensure VCH creation log read/write does not assume relationship between image store path and VM path

[zjs]

See #6665 (comment):

There is a vch.FolderName method that you could call that tells you the directory name of the VM.
It looks like that has been recently changed to only provide the Base name - I am unsure why and @caglar10ur has just left. However this is the call used in lib/install/management/appliance.go:523.

The ImageStores path MAY be the same, but should not be in the case of vSAN - a VM in vSAN MUST have a dedicated namespace and I believe we place the image VMDKS into their own namespace.