FocusZone: undoing a change which caused a regression

[dzearing]

Found a FocusZone regression that was introduced by the fix for #4488.

Say you have some dom structure like:

<FocusZone>
  <button>
    <span>Area</span>
  </button>
</FocusZone>

I am seeing that clicking on the span causes the FocusZone::onClick method to be called where target is the span. This causes FocusZone to track the span, and not the button, as the active element, causing tabIndex on the span to be set to -1, which in turn causes side-effects such as making the span focusable with a mouse and creating visual focus rects on the wrong things.

Undoing the change that introduced this. The original intention of the fix was to reset alignment only when you click on a focusable element. This needs more special consideration and a less intrusive fix.