Fix transitions for image_download and activation

Change-Id: I713ada52eef9d275c7d7596026e178c7382e8335
diff --git a/vendor/golang.org/x/sys/unix/sockcmsg_linux.go b/vendor/golang.org/x/sys/unix/sockcmsg_linux.go
index 6079eb4..8bf4570 100644
--- a/vendor/golang.org/x/sys/unix/sockcmsg_linux.go
+++ b/vendor/golang.org/x/sys/unix/sockcmsg_linux.go
@@ -17,7 +17,7 @@
 	h.Level = SOL_SOCKET
 	h.Type = SCM_CREDENTIALS
 	h.SetLen(CmsgLen(SizeofUcred))
-	*((*Ucred)(cmsgData(h))) = *ucred
+	*(*Ucred)(h.data(0)) = *ucred
 	return b
 }