One-shot timer does not deactivate properly

[bergmansj]

Description

        recording_timer = ui.timer(
            interval=60,
            callback=stop_recording,
            once=True
        )

When recording_timer.deactivate() is called on this timer before the interval runs out, the callback is still called.
I traced this to the self.active property not being checked in the _run_once method. It is properly checked in the _run_in_loop method.

I would like to be able to deactivate a timer, ie avoid the callback happening.
Also, I think it should be possible to cancel the (repeating) timer completely instead of just deactivating its callback.

[falkoschindler]

Thanks for reporting this issue, @bergmansj!

Deactivating should, indeed, prevent the callback from happening. I fixed it in 598b805.

For canceling repeating timers I created a separate pull request #1478. There we can review and discuss this new feature.