Modified Python IVR example to match new arbitrary parameters syntax

Changes to Python IVR example to match the new args/kwargs syntax for arbitrary parameters.

In testing, I found that nested functions are in fact unique per call of the parent function, so duplicate callback handlers are created by ari-py. To fix this, modified example to unsubscribe to events that are subscribed to when queue_up_sound is called again.

Fixed a bug where it was sometimes possible to get multiple timers that overlapped, duplicating sounds during menu playback.