Check for duplicate Content-Length headers in requests

If a duplicate CL header is in the request, we fail the request with a
400 (Bad Request)

Fix a test case that was sending duplicate CL by misstake and would
not fail because of that.
http_CopyResp(struct http *to, const struct http *fm)
{

	CHECK_OBJ_NOTNULL(fm, HTTP_MAGIC);
	CHECK_OBJ_NOTNULL(to, HTTP_MAGIC);
	http_SetH(to, HTTP_HDR_PROTO, "HTTP/1.1");
	to->status = fm->status;
	http_copyh(to, fm, HTTP_HDR_RESPONSE);
}

http_CopyResp(struct http *to, const struct http *fm)
{

	CHECK_OBJ_NOTNULL(fm, HTTP_MAGIC);
	CHECK_OBJ_NOTNULL(to, HTTP_MAGIC);
	http_SetH(to, HTTP_HDR_PROTO, "HTTP/1.1");
	to->status = fm->status;
	http_copyh(to, fm, HTTP_HDR_RESPONSE);
}
