Fix logging of incorrect status codes for disconnected requests (#12580)

The status code of requests must always be set, regardless of client
disconnection, otherwise they will always be logged as 200!.

Broken for `respond_with_json` in
f48792ee.
Broken for `respond_with_json_bytes` in
3e58ce72.
Broken for `respond_with_html_bytes` in
ea26e9a9.

Signed-off-by: Sean Quah <seanq@element.io>