Update the expose-configdrive spec
Update the expose-configdrive spec

Update the expose-configdrive spec to reflect the design changes we had
to made to adapt to what was decided in the Nova project.

Change-Id: I5ceb293a7ca2f5bfd6334fe4c2fa02d4126ed0fa

openstack/ironic-specs,naterh/ironic-specs,NaohiroTamura/ironic-specs,bcornec/ironic-specs