download was being inferred. It's now being set on each and will raise an error if node is provided. Also removed a duplication on params variable.
Stream production wasn't pausing or stopping as asked by protocol.
Was too high due a left over from some bug hunting. 20 is enough to check both zero sized and under/equal/above tag size.
As it's blocking and Twisted already stored everything on a file. -- Related: #8809
-- Resolves: #8809
-- Related: #8809
-- Resolves #8773
