Change SIGUSR1 to be compatible with systemd and SysV init

This patch changes the behavior of SIGUSR1.  Previously USR1 could be
used to halt a running Finit system, similar to BusyBox init.  However,
compatibility with sysvinit and systemd has been deemed more important.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/reboot.c

@@ -206,7 +206,7 @@ int reboot_main(int argc, char *argv[])
 
 	case CMD_HALT:
 		if (do_halt(NULL))
-			do_kill(SIGUSR1, msg);
+			do_kill(SIGUSR2, msg);
 		break;
 
 	case CMD_POWEROFF: