lxd/daemon/image: Adds logic to download image from another cluster node into ImageDownload
lxd/daemon/image: Adds logic to download image from another cluster node into ImageDownload

Allows us to check earlier whether the image is available on another node, before we create the DB entry for our own node (which skews the subsequent locate results).

Signed-off-by: Thomas Parrott <6b778ce645fb0e3dde76d79eccad490955b1ae74@canonical.com>

hallyn/lxd,atxwebs/lxd,atxwebs/lxd,stgraber/lxd,stgraber/lxd,lxc/lxd,stgraber/lxd,atxwebs/lxd,hallyn/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,lxc/lxd,lxc/lxd,atxwebs/lxd,stgraber/lxd,lxc/lxd,lxc/lxd,hallyn/lxd,lxc/lxd,stgraber/lxd,stgraber/lxd,hallyn/lxd,hallyn/lxd