GCS_Failsafe: option to trigger only in AUTO mode.

ArduPlane/system.cpp

@@ -487,7 +487,11 @@ void Plane::check_long_failsafe()
         if (failsafe.state == FAILSAFE_SHORT &&
                    (tnow - failsafe.ch3_timer_ms) > g.long_fs_timeout*1000) {
             failsafe_long_on_event(FAILSAFE_LONG);
-        } else if (g.gcs_heartbeat_fs_enabled != GCS_FAILSAFE_OFF && 
+        } else if (g.gcs_heartbeat_fs_enabled == GCS_FAILSAFE_HB_AUTO && control_mode == AUTO &&
+                   failsafe.last_heartbeat_ms != 0 &&
+                   (tnow - failsafe.last_heartbeat_ms) > g.long_fs_timeout*1000) {
+            failsafe_long_on_event(FAILSAFE_GCS);
+        } else if (g.gcs_heartbeat_fs_enabled == GCS_FAILSAFE_HEARTBEAT &&
                    failsafe.last_heartbeat_ms != 0 &&
                    (tnow - failsafe.last_heartbeat_ms) > g.long_fs_timeout*1000) {
             failsafe_long_on_event(FAILSAFE_GCS);