AP_HAL_ESP32: ensure task is deleted if member proc returns

- FreeRTOS task functions must not return or exit.
- vTaskDelete(NULL) deletes the calling task.

Signed-off-by: Rhys Mainwaring <rhys.mainwaring@me.com>

libraries/AP_HAL_ESP32/Scheduler.cpp

@@ -140,6 +140,9 @@ void IRAM_ATTR Scheduler::thread_create_trampoline(void *ctx)
     AP_HAL::MemberProc *t = (AP_HAL::MemberProc *)ctx;
     (*t)();
     free(t);
+
+    // delete the calling task
+    vTaskDelete(NULL);
 }
 
 /*