Add NoSQL database support for metering.

- Add two attributes to indicate whether NoSQL is used for metering
  database and the port used for NoSQL database.
- When database type is DB2, only NoSQL is supported and the SQL
  connection is not same to the one SQLAlchemy-based.

Change-Id: Icff805cee8e078f99ff46a59e290da60d2f9bb29
Merge "Add NoSQL database support for metering."
Add notification_topics attribute to network

This change adds the notification_topics attribute for the network
cookbook.  This commit will need to be merged before
https://review.openstack.org/#/c/75910/.

Change-Id: I65d24bf5c981e3540b1a530f7343983b6c513cc2