Copy glance_image_metadata when cloning volumes.

When cloning a volume we were not capturing/copying
the glance_image_metadata from the source volume.

This change implements a copy_image_metadata_from_vol_to_vol.
So now we can clone bootable volumes without going back to glance
or messing with them otherwise, they're just ready to be booted.

Fixes bug: 1115634

Change-Id: I859bb2550267c6a5142e85ec89f1c7ff885588ac
Merge "Copy glance_image_metadata when cloning volumes."