Add a new import method called glance-download
that implements a glance to glance download in
a multi-region cloud with a federated Keystone.
This method will copy the image data and
selected metadata to the target glance, checking
that the downloaded size match the "size" image
attribute in the source glance.
Implements: blueprint glance-download-import
Co-Authored-By: Victor Coutellier <victor.coutellier@gmail.com>
Change-Id: Ic51c5fd87caf04d38aeaf758ad2d0e2f28098e4d