Transaction isolation override in confluence.cfg.xml does not apply to bootstrap checks

Customers can specify custom hibernate configuration options in their confluence.cfg.xml, and we have validation code in the bootstrap system to check that these options result in a working hibernate environment. Unfortunately, the code in this validation layer is not using all the properties that a customer can specify in their config, meaning that some properties (like hibernate.connection.isolation) are not applied while validating the DB.

We need to make it so customer overrides of the transaction isolation level apply during bootstrap too. We also need to fix this so that we check all the properties on bootstrap, not just a handful.