Change to messagingv2 for oslo_messaging_notifications.driver

The oslo.messaging docs on the notification messaging driver
says that "messaging" (1.0) is a legacy format and you should
use messagingv2 unless otherwise required for that old format.

By default we should be testing with messagingv2.

Change-Id: I3031afe7551a0c8dde46e1ccfacff445fb68e122
diff --git a/lib/cinder b/lib/cinder
index 767fd00..c17cea0 100644
--- a/lib/cinder
+++ b/lib/cinder
@@ -315,7 +315,7 @@
     fi
 
     if is_service_enabled ceilometer; then
-        iniset $CINDER_CONF oslo_messaging_notifications driver "messaging"
+        iniset $CINDER_CONF oslo_messaging_notifications driver "messagingv2"
     fi
 
     if is_service_enabled tls-proxy; then