Plane: use scheduler ticks in place of mainloop_count

ArduPlane/ArduPlane.cpp

@@ -126,9 +126,6 @@ void Plane::loop()
     G_Dt                     = (timer - perf.fast_loopTimer_us) * 1.0e-6f;
     perf.fast_loopTimer_us   = timer;
 
-    // for mainloop failure monitoring
-    perf.mainLoop_count++;
-
     // tell the scheduler one tick has passed
     scheduler.tick();
 

ArduPlane/Plane.h

@@ -741,9 +741,6 @@ private:
         // System Timers
         // Time in microseconds of start of main control loop
         uint32_t fast_loopTimer_us;
-        
-        // Counter of main loop executions.  Used for performance monitoring and failsafe processing
-        uint16_t mainLoop_count;
     } perf;
 
     struct {

ArduPlane/failsafe.cpp

@@ -16,14 +16,15 @@
  */
 void Plane::failsafe_check(void)
 {
-    static uint16_t last_mainLoop_count;
+    static uint16_t last_ticks;
     static uint32_t last_timestamp;
     static bool in_failsafe;
     uint32_t tnow = micros();
 
-    if (perf_info.get_num_loops() != last_mainLoop_count) {
+    const uint16_t ticks = scheduler.ticks();
+    if (ticks != last_ticks) {
         // the main loop is running, all is OK
-        last_mainLoop_count = perf_info.get_num_loops();
+        last_ticks = ticks;
         last_timestamp = tnow;
         in_failsafe = false;
         return;