add a rpc class for other notification queues

Cinder has a default notification queue "notification.info" for ceilometer, we know "notification" is given in cinder.conf (topics = notifications).

Now I need an other notification queue for resource statistics while "notification.info" is also for ceilometer. What am I going to do?
cinder/rpc.py doesn't work well right now.

I will give a rpc class,. If someone wants to create notification queue, he can have a rpc object. Therefore, other notifications can be created.