lxd/images: Fix auto image updates
lxd/images: Fix auto image updates

Instead of all cluster nodes updating the same image, a single node is
selected for this job. Afterwards, the image will be distributed to
the other nodes.

Signed-off-by: Thomas Hipp <5f82c492b3b00e427412d216ce820707a10c51ce@canonical.com>

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