Remove /dev/diag node on user builds.

Change-Id: Ia0a61d8a5e2292f8fc0d465cc7ccf44c80fda38f
diff --git a/init.hammerhead.diag.rc.user b/init.hammerhead.diag.rc.user
index ce0a202..78d18e5 100644
--- a/init.hammerhead.diag.rc.user
+++ b/init.hammerhead.diag.rc.user
@@ -1 +1,4 @@
 # This file gets copied as /init.hammerhead.diag.rc
+
+on boot
+    rm /dev/diag