Disable ceilometer.compute.nova_notifier driver

It appears that the ceilometer nova notification driver is causing
nova-compute to hang.  The last thing nova-compute logs before hanging
is a line from this driver.  At the very least the ceilometer nova
notification keeps stacktracing.

Change-Id: Ic375272b751159a64777ca73c1b64515195aacfb
Related-Bug: #1221987
diff --git a/lib/nova b/lib/nova
index 9b766a9..577c260 100644
--- a/lib/nova
+++ b/lib/nova
@@ -513,7 +513,6 @@
         iniset $NOVA_CONF DEFAULT instance_usage_audit "True"
         iniset $NOVA_CONF DEFAULT instance_usage_audit_period "hour"
         iniset $NOVA_CONF DEFAULT notify_on_state_change "vm_and_task_state"
-        iniset_multiline $NOVA_CONF DEFAULT notification_driver "nova.openstack.common.notifier.rpc_notifier" "ceilometer.compute.nova_notifier"
     fi
 
     # Provide some transition from ``EXTRA_FLAGS`` to ``EXTRA_OPTS``