Adds Flavor CRUD CLI commands

Adds tests for Flavor CRUD CLI commands.

Implements: blueprint tripleo-flavors-cli
https://blueprints.launchpad.net/python-tuskarclient/+spec/tripleo-flavors-cli

Change-Id: If00f281b6287e34773dacd43af849b221a93cd8d
Merge "Adds Flavor CRUD CLI commands"