Messages about overriding content and/or version URLs on STDOUT spoil JSON output

[bwarden]

If we override the content or version URLs using -u, -c, or -v, we print out a message on STDOUT warning about it:

swupd-client/src/swupd_lib/globals.c

Lines 553 to 572 in ec4a272

	case 'u':
	print("Overriding version and content URLs with %s\n", optarg);
	set_version_url(optarg);
	set_content_url(optarg);
	return true;
	case 'P':
	err = str_to_int(optarg, &globals.update_server_port);
	if (err < 0 || globals.update_server_port < 0) {
	error("Invalid --port argument: %s\n\n", optarg);
	return false;
	}
	return true;
	case 'c':
	print("Overriding content URL with %s\n", optarg);
	set_content_url(optarg);
	return true;
	case 'v':
	print("Overriding version URL with %s\n", optarg);
	set_version_url(optarg);
	return true;

In most cases, this is probably fine. But if we've been given -j for JSON output, we really should only be outputting valid JSON strings. We should probably move these (and any other) warnings to STDERR.

This will likely affect test cases, too.