fix(simu): simulator shutdown (#6196)

Co-authored-by: philmoz <phil.a.mitchell@gmail.com>

radio/src/tasks/mixer_task.cpp

@@ -48,7 +48,6 @@ static mutex_handle_t mixerMutex;
 // mixerTaskStart() has been called.
 static bool _mixer_started = false;
 static bool _mixer_running = false;
-static bool _mixer_exit = false;
 
 void mixerTaskLock()
 {
@@ -93,14 +92,9 @@ void mixerTaskStop()
   mixerTaskUnlock();
 }
 
-void mixerTaskExit()
-{
-  _mixer_exit = true;
-}
-
 bool mixerTaskRunning()
 {
-  return _mixer_running && !_mixer_exit;
+  return _mixer_running;
 }
 
 volatile uint16_t timeForcePowerOffPressed = 0;
@@ -144,7 +138,7 @@ void mixerTask()
   gyroInit();
 #endif
 
-  while (!_mixer_exit) {
+  while (task_running()) {
 
     int timeout = 0;
     for (; timeout < MIXER_MAX_PERIOD; timeout += MIXER_FREQUENT_ACTIONS_PERIOD) {

radio/src/tasks/mixer_task.h

@@ -53,15 +53,6 @@ void mixerTaskStart();
 //
 void mixerTaskStop();
 
-
-// exit the mixer forever.
-//
-// This is probably only useful for simulations as it is not needed to really
-// exit the task under any normal conditions. There are no guarantees as to when
-// the exit will happen, only that it will eventually happen.
-//
-void mixerTaskExit();
-
 // hint at whether or not the mixer task should be running
 //
 // Please note: there is no guarantee on anything, this is just returning