Comment 2 for bug 532366

                switch (mode) {
                case REBOOT:
                        args[i++] = "-r";
                        break;
                case HALT:
                        args[i++] = "-h";
                        break;
                case POWEROFF:
                        args[i++] = "-h";
                        args[i++] = "-P";
                        break;
                }

The HALT case should pass the -H (called as halt) argument to shutdown, just as the POWEROFF case passes -P