Perform a reload on objects when Refreshing them

Previously, it was possible for an object to be "refreshed" with a stale cached state from the current thread's context.

This ensures a check against the database is performed as well.

Resolves #1562.

osu.Game/Database/DatabaseBackedStore.cs

@@ -35,6 +35,7 @@ namespace osu.Game.Database
 
             var id = obj.ID;
             obj = lookupSource?.SingleOrDefault(t => t.ID == id) ?? context.Find<T>(id);
+            context.Entry(obj).Reload();
         }
 
         /// <summary>