Add support for injecting extra-specs into flavors

Building on the ability to create flavors to describe the hardware
your cloud has available, we need the ability to inject extra_specs
into the flavors when they are created to save operators having to
do so by hand.

Change-Id: Ib1339d0dd60c5fb4669bb10c5543e5155e86fe1f
Merge "Add support for injecting extra-specs into flavors"