Make light change only when the message contents change.

Change-Id: If81caf2107227ecb527401136ca6f9fa261d52ac
diff --git a/y2018/BUILD b/y2018/BUILD
index 19284e8..67ad583 100644
--- a/y2018/BUILD
+++ b/y2018/BUILD
@@ -39,6 +39,7 @@
         "joystick_reader.cc",
     ],
     deps = [
+        ":status_light",
         "//aos/common:time",
         "//aos/common/actions:action_lib",
         "//aos/common/logging",