Comment 12 for bug 1495895

OK, updating the libvirt-qemu apparmor abstraction resolves this issue:

# diff -u libvirt-qemu.orig libvirt-qemu
--- libvirt-qemu.orig 2015-09-16 18:14:46.013741000 +0000
+++ libvirt-qemu 2015-09-16 18:14:34.001741000 +0000
@@ -144,6 +144,10 @@

   # for rbd
   /etc/ceph/ceph.conf r,
+ /usr/lib/x86_64-linux-gnu/qemu/block-rbd.so rm,
+
+ # for curl
+ /usr/lib/x86_64-linux-gnu/qemu/block-curl.so rm,

   # for access to hugepages
   owner "/run/hugepages/kvm/libvirt/qemu/**" rw,

now, we can attach an rbd volume:

root@juju-devel3-machine-14:~# virsh list
 Id Name State
----------------------------------------------------
 2 instance-00000001 running

root@juju-devel3-machine-14:~# virsh qemu-monitor-command --hmp instance-00000001 'info block'
drive-virtio-disk0: /var/lib/nova/instances/1b1ecffb-bddc-4825-8adb-3dce71fbcc57/disk (qcow2)
    Cache mode: writeback, direct
    Backing file: /var/lib/nova/instances/_base/0d0b68a8b7de02d81bdb0b644132349a8663ed1a (chain depth: 1)

drive-virtio-disk1: rbd:cinder-ceph/volume-da89c042-0628-4630-9d95-4624452d346c:id=nova-compute:key=AQDUdflVYhZ4FhAAmT/7O1S3bUpOHaAFBqq1SA==:auth_supported=cephx\;none:mon_host=10.5.29.172\:6789\;10.5.29.173\:6789\;10.5.29.174\:6789 (raw)
    Cache mode: writeback, direct