Migrate the negative tests to use auto-gen framework

The framework for generating negative tests from json schemas now exists. This blueprint is to track progress migrating existing negative tests to use that framework. Since the framework is json-only, the existing xml negative tests will remain. Here are the steps to migrate a negative test file:

1. Copy the file xxx_negative.py to xxx_negative_xml.py and remove everything related to JSON
2. Create a new schema in tempest/etc/schemas/.. based on the service type and api being tested
3. Replace xxx_negative.py with a class based on the auto-gen framework.

Note that there are some negative tests that cannot be expressed in the auto-gen framework. In that case, such tests should be preserved in the file being migrated.

Given the state of flux with nova api v2/v3 it would probably be better to focus on the other services. We may find a way to get schemas for nova without having to write all of them in tempest.