Work on improving slave reaction to a missing master

* Slave: only start listening on our connection port when we have a connected
  master.  Disconnect listening when master goes away
* Slave: Stop proxying logs when master goes away
* Slave: Work on improving retries when master isn't there.  This isn't
  perfect yet... it won't sit and keep retrying like it should
* LogController: add support for calling proxyToMaster without an argument to
  remove an existing proxy
* Rewind: Remove old Listener object