For both the file and virtual_disk resource, Stat is used during read,
but if Stat returns an error, read() will return that error. In doing
so, if a resource is deleted manually, the TF user would then not be
able to destroy the resource because the read would block the Delete()
call. With this patch, read() will only return an error if that error
is NOT a DatastoreNoSuchFileError.
* Adding File Resource for vSphere provider
Allows for file upload to vSphere at specified location. This also
includes update for moving or renaming of file resources.
* Ensuring required parameters are provided