Add an option to send 'a' repeatedly

Change-Id: I81239d802035ecfb760c483b8b0d83c66a643f5d
diff --git a/y2019/vision/target_sender.cc b/y2019/vision/target_sender.cc
index 4c14969..2801c61 100644
--- a/y2019/vision/target_sender.cc
+++ b/y2019/vision/target_sender.cc
@@ -390,6 +390,7 @@
 
             switch (calibration.camera_command) {
               case CameraCommand::kNormal:
+              case CameraCommand::kAs:
                 break;
               case CameraCommand::kUsb:
                 return 0;