Fixes for the surprising case where AuraRenderingService.rerender's "this" is not $A.renderingService.

This was a bug in 98105285, where when a renderer invoked $A.rerender, "this" wasn't the rendering
service object but instead was $A.

@rev dchasman,gtorres@
@bug W-2113046@
Merging origin/fabbott/master-pending-rerender_this into master