Updated openstack-common.conf and remove outdated modules. Ran update script in oslo-incubator to generate modules in the mistral/openstack and tools directories. Sqlalchemy backend has changed significantly in oslo-incubator. Refactored mistral db api to address these changes and updated the base test class DbTestCase accordingly. Change-Id: I61327c33c0c8bc616af5e7633634461a2d7ac691 Implements: blueprint mistral-sync-with-incubator