commander: reboot/shutdown usability fixes

- always check with state machine before reboot/shutdown
 - respect BOARD_HAS_POWER_CONTROL (shutdown from command, low battery, power button)
 - px4_shutdown_request add optional delay and always execute from HPWORK
 - px4_shutdown_request split out px4_reboot_request

platforms/qurt/src/px4/common/tasks.cpp

@@ -107,12 +107,6 @@ static void *entry_adapter(void *ptr)
 	return NULL;
 }
 
-void
-px4_systemreset(bool to_bootloader)
-{
-	PX4_WARN("Called px4_system_reset but NOT yet implemented.");
-}
-
 px4_task_t px4_task_spawn_cmd(const char *name, int scheduler, int priority, int stack_size, px4_main_t entry,
 			      char *const argv[])
 {