Function kwait::backoff_until

pub fn backoff_until<F>(
    f: F, 
    backoff: Box<dyn BackoffManager>, 
    sliding: bool, 
    stop_ch: Receiver<bool>
) where
    F: Fn(), 

backoff_until loops until stop channel is closed, run f every duration given by BackoffManager.

If sliding is true, the period is computed after f runs. If it is false then period includes the runtime for f.