Use Centralized database for caching

We use two different database(s) for glance. One is centralized database managed by oslo.db (default is MySql) for storing information related to regular operations and sqlite for storing information about caching related operations. Even though sqlite database is only created if we enable cache middleware we still need to maintain it along with centralized database. Also glance caches are local to each controller node (glance api service), so in case of multiple glance services running we have multiple sqlite database(s) operational.