tests: Disable test_clustering_image_replication
tests: Disable test_clustering_image_replication

This test is based on incorrect assumption, we should turn it off until
we have #8641 fixed, then can be re-enabled.

Signed-off-by: Stéphane Graber <089afc6d81f66f1168a9849e15660feae286e024@ubuntu.com>

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