Fix bug where attachments would not retain position if just rotated and not moved.

This was because we were not setting AttachedPos in SOG.UpdateGroupPositionPR, unlike UpdateGroupPosition

OpenSim/Region/Framework/Scenes/SceneObjectGroup.cs

@@ -2895,6 +2895,11 @@ namespace OpenSim.Region.Framework.Scenes
                 m_scene.PhysicsScene.AddPhysicsActorTaint(actor);
             }
 
+            if (IsAttachment)
+            {
+                m_rootPart.AttachedPos = pos;
+            }
+
             AbsolutePosition = pos;
 
             HasGroupChanged = true;