Draggable Tests: fix current JSCS violations in draggable_test_helpers.js
Draggable Tests: fix IE offset tests affected by focus issues.

Calling element.focus() causes scroll in IE. In order to correctly test scroll behavior,
we must rely on the actual calculated offset instead of the helper offset to ensure
cross browser test consistency.
Draggable Tests: fix IE scroll tests affected by focus issues.

Calling element.focus() causes scroll in IE. In order to correctly test scroll behavior,
we must calculate scrollTop on the drag event, before .focus is called.