The upstream gcp aggressively closes the connection once it has
received Content-Length bytes. However the @google-cloud/storage
module doesn't handle this well and emits no event in this case.
We were setting Content-Length because it's slightly more
efficient and was important for our download progress
bar (not anymore). The download should function fine without
setting the Content-Length, and allows the storage stream to finish
before closing the upstream socket.
