Stop prims that get non-physical. Fixes Mantis#2859.

OpenSim/Region/Environment/Scenes/SceneObjectPart.cs

@@ -1450,6 +1450,13 @@ if (m_shape != null) {
                             }
                         }
                     }
+
+                    if (!UsePhysics)
+                    {
+                        // reset velocity to 0. Without that, the client thinks the prim still has velocity and
+                        // continues to interpolate its position along the old velocity-vector.
+                        Velocity = new Vector3(0, 0, 0);
+                    }
                 }
                 m_parentGroup.Scene.PhysicsScene.AddPhysicsActorTaint(PhysActor);
             }