#38 Failure changing HVAC state is not properly reported

[Vadim Tkachenko]

Followup to bug #864816:

If the actuator fails to change the HVAC state, the
only place where it is visible is the logs. People
don't read logs. This must be changed and a clear
notification must be issued.

The root cause of it is that the control logic is
asynchronous. Another painful change.