Disable sending "Connection: keep-alive" header from server

[NiteshKant]

HttpConnectionHandler adds a "Connection: keep-alive" header if the client has requested keep-alive connections (default for HTTP 1.1 or presence of "Connection: keep-alive" header in the request)

For HTTP 1.1 keep-alive is the default so sending this header is not required. On the other hand, if the client request a close (Connection: close header) then we should reply with the same.

Removing Connection: keep-alive header makes simple applications (benchmarks) faster as there is less data to send.