Export volume metadata to new instances.

Instances that are booted from volume currently miss out on glance
metadata that instances booted from images receive. By extracting
that data and passing it on in the create request we make it
available to both sorts of instance boot, fixing bug 1175571.

Change-Id: I8c01ba3065a909ca8e1805db9a10a423b10fe289
Merge "Export volume metadata to new instances."