BHV-1576: VideoPlayer: Unexpected Overlap between Tooltip and Popup List

### Issue:
In the VideoPlayer Sample, there is a contextual popup decorator wrapped inside a tooltip decorator. When they both show, the tooltip unexpectedly overlaps the popup list.
### Fix:
Add an onShowingChanged event handler to the contextual popup, and mute/unmute the tooltip based on whether the popup is showing

Enyo-DCO-1.1-Signed-off-by: Krishna Rangarajan <krishna.rangarajan@lge.com>