fix a nasty sleep bug: we weren't stopping our old mesh service

so it would kinda keep living (along with the recreated one) when we
come back from sleep.

src/MeshBluetoothService.cpp

@@ -332,6 +332,7 @@ BLEService *createMeshBluetoothService(BLEServer *server)
 void destroyMeshBluetoothService()
 {
     assert(meshService);
+    meshService->stop();
     delete meshService;
 
     meshFromNumCharacteristic = NULL;