Weird, it wasn't working when I tried it on my world but when I recreated it to show the steps it worked. Oops!
I don't know how to delete the issue though.Â
This happened to me just now in the latest snapshot (15w45a). I got the bug where the horse doesn't load chunks and when I arrived next to the unloaded chunks, I couldn't dismount to so I dc'ed and reconnected and there was 2 horses.
Yeah, my bad, should have tried to recreate it before opening the issue 😞