AP_HAL_Linux: Scheduler reboot fix

exit from the autpilot when reboot is commanded.
The software assumes that the code is being
launched in an infinite loop thereby an exit
will make it reboot.

libraries/AP_HAL_Linux/Scheduler.cpp

@@ -384,7 +384,7 @@ void LinuxScheduler::system_initialized()
 
 void LinuxScheduler::reboot(bool hold_in_bootloader) 
 {
-    for(;;);
+    exit(1);
 }
 
 void LinuxScheduler::stop_clock(uint64_t time_usec)