BHV-728: Prevent sending onSpotlightContainerLeave when not actually leaving container.

Issue
-------
The `onSpotlightContainerLeave` event is sent even when focus does not actually leave the container; this occurs on 5-way move where there is nothing spottable outside of the container in the intended 5-way direction.

Fix
----
In the `_focusLeave` method, we guard against this case by comparing the `lastFocusedChild` and the subsequent control that is being spotted.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>