42711 multiple log messages

- Bump Cocoalumberjack to version 2.0.0-rc
- Set up test logging inside dispatch_once block
Having logging turned on for tests gives us more knowledge about test failures that may be platform dependant, or test system dependant. Also with plans to run against development builds of DBCore I think it's a must have.

Since this sets up global logging, it should be the test case's duty to add and remove additional loggers if they desire, since its directly related to their test and they should clean up after themselves.

Another thing to consider with `removeAllLoggers` is that does it enforce that log messages would have completed being written before the logger gets deallocated. Logging is asynchronous unless it is an error message, unless the framework will also guarantee that messages will be flushed before the logger is removed and deallocated, I don't think it is the solution we should be going for.