Fix issue with function staying ON in a fast running chaser

... aaaand last one in this PR salvo :)


Problem with a function staying ON:
- Have a "classic" chaser (with some scenes in it)
- Create a second chaser containing this chaser + any other function, with duration set to 0
- go to operate mode, start the second chaser and then stop it
- the first function of the "classic" chaser will stay ON.

I stumble upon this with an audiotriggers + singleshot chaser, but it is easier to reproduce with the steps above.

Here the issue is fixed by a different handling of the 'stopped' or 'is running' steps

- isRunning() means the function is between preRun() and postRun()
- stopped() means the function is either stopped or in its way to being stopped. This can happen before preRun() has been called.