Improve bot initialization

[aomerk]

Instead of spawn-and-wait'ing bot initializations, lifecycle is now like the following:

• call go agent.Initialize() at handleStatusRunning
• call SetInitialized() once initialization is completed
  • SendEvaluateXXX will skip if !agent.IsInitialized()
• call agent.Close() on init errors
  • at some point some routine will call ap.discardAgent(agent) because the agent will be closed
  • pool will try deploying it again
• publishes the combiner subscription message in initialize method
  • it used happen in handleStatusRunning, but that thing won't have the alert config from the init response anymore