klighd: fixed inset calculation.

Previously insets were calculated wrong by offsetting all insets too
much when renderings were inside renderigns with offsets. For the server
this is an invisible fix, as all Piccolo-related rendering code do not
directly use these insets, LSP rendering however directly use the insets
for Sprotty, which are now fixed.

plugins/de.cau.cs.kieler.klighd/src/de/cau/cs/kieler/klighd/microlayout/PlacementUtil.java

@@ -1570,6 +1570,9 @@ public static void calculateInsets(final KRendering rootRendering, final KInsets
             if (currentRendering instanceof KContainerRendering) {
                 currentParent = (KContainerRendering) currentRendering;
                 currentBounds = bounds;
+                // Reset current position to avoid adding top/left insets multiple times.
+                currentBounds.x = 0;
+                currentBounds.y = 0;
             }
         }