The Stream pointer just acts as a key in the Request object. There is no
good use-case to modify a stream from a pointer retrieved from the
Request, make it const. This allows pipeline handlers to better express
that the Stream pointer is retrieved in a Request should just be treated
as a key.
Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>