Fix BasePolarisAuthenticator to throw service exception during persistence errors

[collado-mike]

In cases when the persistence store in unavailable or experiencing errors, the authenticator catches exceptions and causes the service to incorrectly return 401. These exceptions are almost never retried by upstream clients or reverse proxies, so intermittent failures will cause clients to simply shut down. This correctly throws ServiceFailureExceptions in these cases and adds a unit test specifically for the BasePolarisAuthenticator