cloud: drop VMDK output image for cloud
We added this so we could eventually use the VMDK to optimize our
uploads to AWS but it turns out the VMDK created by imagefactory
isn't in the right format anyway.
```
SNAPSHOTTASKDETAIL 0.0 VMDK deleted ClientError: Disk validation failed [Unsupported VMDK File Format]
```
Let's drop them for now.
Signed-off-by: Dusty Mabe <dusty@dustymabe.com>