Bug 2189412

.Client no longer resets the connection for an incorrect `Content-Length` header field value Previously, when returning an error page to the client, for example, a 404 or 403 condition, the `</body>` and `</html>` closing tags were missing, although their presence was accounted for in the request’s `Content-Length` header field value. Due to this, depending on the client, the TCP connection between the client and the Rados Gateway would be closed by an RST packet from the client on account of incorrect Content-Length header field value, instead of a FIN packet under normal circumstances. With this fix, send the `</body>` and `</html>` closing tags to the client under all the required conditions. The value of the `Content-Length` header field correctly represents the length of data sent to the client, and the client no longer resets the connection for an incorrect Content-Length reason.