Return 400 for decoding exceptions

Netty does not send any response for exceptions occurred while decoding HTTP Query requests. https://gist.github.com/chinmay-gupte/c871758bdc24833136e3.
Fixed this and made it to send `400` for decoding exceptions and close the connection.
https://gist.github.com/chinmay-gupte/33c5a539357a20b0a914