MINOR: http-ana: Use a dedicated function to send a response from an http reply

MINOR: http-ana: Use a dedicated function to send a response from an http reply

The http_reply_message() function may be used to send an http reply to a
client. This function is responsile to convert the reply in HTX, to push it in
the response buffer and to forward it to the client. It is also responsible to
terminate the transaction.

This function is used during evaluation of http return rules.