fix steed eating feedback

fix steed eating feedback

     <Someone> reported that riding a steed into a magic portal can
give "steed is still eating" message, feedback normally used to explain why
you can't go down stairs.  Rather than preventing portals from activating
in that situation, just force the meal to be finished in order to suppress
the message.  Proper fix is probably to prevent all steed movement while
eating, but that would most likely result in no one ever riding again.