Make the catalog flavor-aware

This patch adds the knowledge of flavors to the catalog. When a new
queue is registered, if a flavor is passed, it'll get the pool from the
flavor record. If flavor is not passed, it'll preserve the previous
behavior.

Partially Implements blueprint: marconi-queue-flavors

Change-Id: Idcf5a0215699269f29df793169ff21fc6435f3b2