Force reloading of the session after destroy

Use load_for_write! to ensure a refresh of the session object.
This way the new session_id and the empty data will be stored properly.
E.g. in the case of the session cookie store this means that a new
digest will be returned to the user.

actionpack/lib/action_dispatch/request/session.rb

@@ -72,7 +72,10 @@ module ActionDispatch
         options = self.options || {}
         new_sid = @by.send(:destroy_session, @env, options[:id], options)
         options[:id] = new_sid # Reset session id with a new value or nil
+
+        # Load the new sid to be written with the response
         @loaded = false
+        load_for_write!
       end
 
       def [](key)