Null hostfailworker

Reordered statements in Spawn constructor to prevent the leaked partially initialized instance from causing NPE during startup.

I'm pretty confident about the change to instantiate HostFailWorker before SpawnMQ and start FailHostTask schedule after. After that, SpawnMQ threw NPE when calling SpawnBalancer -- for the same reason as HostFailWorker, so I moved SpawnBalancer init to before SpawnMQ. I'm less confident of that change. Though everything tested OK on local stack. Could really use review by folks more familiar with the interdependencies of these components.