EUCA-9190: CC requests not being throttled.

CC has a fixed number of listener threads, 8, currently.

The CLC has previously, and must restore, the local throttling of the number of concurrent requests. The alternative implies that requests have the illusion their channel is open (because its session is indeed ESTABLISHED), but may never have the opportunity to send their requests before timing out.

The failure mode of timing out prior to connect manifests as delayed dispatch of any buffers which have been asynchronously written to the channel, possibly only being part of the request.
EUCA-9190: Handle sensor listener and processing of sensor data in a separate thread

- Handle one at a time execution of sensor listener
- Process sensor data in a separate thread from the I/O thread, which is a restricted.
- Hijack message processing from the callback to ensure the one-at-a-time semantic is preserved.
EUCA-9190: Add @Periodic annotation to distinguish user-generated-event listener execution.
EUCA-9190: Update default value for cluster request workers, adjust log level to be sane.
EUCA-9190: Call the underlying fire method, not the no-op.