VMware: Volume from non-streamOptimized image

VMware: Volume from non-streamOptimized image

Volume creation from non-streamOptimized images (preallocated/thin/sparse)
has following problems:

1) Sparse vmdk image is not converted to appropriate virtual disk type
   suitable for attaching to a nova instance.
2) The adapter type in image meta-data is ignored while creating volumes.
3) The vmware:vmdk_type extra_spec property is ignored.
4) Virtual disk extent operation is called with a wrong parameter which
   might result in unwanted disk provisioning type conversion.

This patch fixes the first 3 problems using the following workflow:

a) Create a disk-less backing.
b) Create a virtual disk (single flat extent) from the non-streamOptimized
   image
c) Attach the virtual disk to the backing
d) Clone the backing (if needed) to perform disk provisioning type conversion

Closes-Bug: #1287176
Closes-Bug: #1287185
Closes-Bug: #1284284
Change-Id: Ib7e9fae81d69d2fe490a4b603337f3d5cee1138c