make materials save to grid less async on manual backup or shutdown

OpenSim/Region/OptionalModules/Materials/MaterialsModule.cs

@@ -154,8 +154,20 @@ namespace OpenSim.Region.OptionalModules.Materials
                         m_changed.Remove(fm);
                     }
                 }
+            }
 
             if(toStore.Count > 0)
+            {
+                if (forcedBackup)
+                {
+                    foreach (FaceMaterial fm in toStore)
+                    {
+                        AssetBase a = MakeAsset(fm, false);
+                        m_scene.AssetService.Store(a);
+                    }
+                }
+                else
+                {
                     Util.FireAndForget(delegate
                     {
                         foreach (FaceMaterial fm in toStore)
@@ -166,6 +178,7 @@ namespace OpenSim.Region.OptionalModules.Materials
                     });
                 }
             }
+        }
 
         private void EventManager_OnObjectAddedToScene(SceneObjectGroup obj)
         {