Better way to prevent snapping to area fill

This also prevents are hover behavior during node dragging,
while allowing snapping to vertex fill.

css/map.css

@@ -940,10 +940,11 @@ text.point {
 }
 
 /* Ensure drawing doesn't interact with area fills. */
-.mode-add-point .area,
-.mode-draw-line .area,
-.mode-draw-area .area,
-.mode-add-line .area,
-.mode-add-area .area {
-    pointer-events: visibleStroke;
+.mode-add-point .area.fill,
+.mode-draw-line .area.fill,
+.mode-draw-area .area.fill,
+.mode-add-line .area.fill,
+.mode-add-area .area.fill,
+.behavior-drag-node .area.fill {
+    pointer-events: none;
 }

js/id/behavior/drag_node.js

@@ -74,14 +74,7 @@ iD.behavior.DragNode = function(context) {
             return {};
         }
 
-        var datum = d3.event.sourceEvent.target.__data__,
-            target = d3.select(d3.event.sourceEvent.target);
-
-        if (datum && !target.classed('fill')) {
-            return datum;
-        }
-
-        return {};
+        return d3.event.sourceEvent.target.__data__ || {};
     }
 
     function move(entity) {