Introduced files to block steamos actions as we don't need updating

files/system/usr/bin/steamos-polkit-helpers/steamos-update

@@ -0,0 +1,8 @@
+#!/bin/bash
+
+# Exit immediately on error and throw an error
+# when using undefined variables
+set -eu
+
+# Run the steamos-update script
+exec /usr/bin/steamos-update "$0"