CraftBukkit caused a regression here by making unloading chunks not
have a ticket added and returning unloaded future.
This caused entities who were killed in same tick their chunk is unloading
to not be able to be removed from the chunk.
This then results in dead entities lingering in the Chunk.
Combine that with a buggy detail of the previous implementation of
the Dupe UUID patch, then this was the likely source of the "Ghost entities"
