Sync image when first instance launched

When instance launched in the cascaded openstack and no corresponding
image found, then the image will be synced to cascaded firstly, then
vm is launched by this image.
Next time when launching instance using the same image, there is no
need to sync.

Implements: blueprint sync-image-first-vm-launch
Change-Id: I51e43065c7b0ed2a59f44aca5ab9c06a8a858945