Watchdog required when currentState != desiredState

[shortbloke]

DogDoor stopped opening today, even though desiredState=OPEN. Not sure why.

1. Examine code and determine when/why this could occur and fix it (if possible)
2. Add a watchdog timer to reset the device if it fails to reach the desired state within a fixed time interval.

The problem, when it occurred, was fixed by sending a remote reset command, so the device was still working through the main loop.