Update driver metadata definitions to Juno

vmware and libvirt support different hw_vif_model settings.
This patch updates them so that each namespace can specify
the models they support.

vmware api is updated with the vmware_disktype

Change-Id: Iec5901097c9621a052a930b99d5cbe7872d4f3ff
Closes-bug: 1370767
(cherry picked from commit ebafdbeef6420d0fcc4922f245956096ca9e50b3)