MINOR: http-ana: Rely on http_reply_and_close() to handle server error

The http_server_error() function now relies on http_reply_and_close(). Both do
almost the same actions. In addtion, http_server_error() sets the error flag and
the final state flag on the stream.
diff --git a/include/proto/http_ana.h b/include/proto/http_ana.h
index 6bef553..57fd881 100644
--- a/include/proto/http_ana.h
+++ b/include/proto/http_ana.h
@@ -48,7 +48,7 @@
 void http_check_response_for_cacheability(struct stream *s, struct channel *res);
 void http_perform_server_redirect(struct stream *s, struct stream_interface *si);
 void http_server_error(struct stream *s, struct stream_interface *si, int err, int finst, const struct buffer *msg);
-void http_reply_and_close(struct stream *s, short status, struct buffer *msg);
+void http_reply_and_close(struct stream *s, short status, const struct buffer *msg);
 void http_return_srv_error(struct stream *s, struct stream_interface *si);
 struct buffer *http_error_message(struct stream *s);