Disposal fixes

Removes the deliverychute entirely from the machinery ticker and updates his flush() proc with his parent that I fixed long time ago. Because someone though that copypasting was the best idea to make new machines.

Anyways I'm not planning to keep touching this for a while, if you want to remove the copypasta, please, do it.
If there's a wall on top of the exit of a disposal pipe, the disposal pipe will now shoot the stuff to the wall anyways because being stuck in the holder inside of pipe sucks.