Add support for vmdk files as glance images

* Adds support for vmdk files as glance images in upload_image function
* Set default image url to use for vsphere driver in stackrc
* Now using a more stable url

Change-Id: If6d45bc8dfd3c812ded5e1bcf69ad7ebd9b64f34
Merge "Add support for vmdk files as glance images"