Convert openstack image to qcow2 0.10 compat

Signed-off-by: Maria Shaldibina <mshaldibina@pivotal.io>
Signed-off-by: Kris Hicks <krishicks@gmail.com>
Make instance type configurable in Openstack BATs

via BOSH_OPENSTACK_INSTANCE_TYPE

Signed-off-by: Kris Hicks <krishicks@gmail.com>