Fix transitions for image_download and activation

Change-Id: I713ada52eef9d275c7d7596026e178c7382e8335
diff --git a/vendor/golang.org/x/sys/unix/ztypes_darwin_386.go b/vendor/golang.org/x/sys/unix/ztypes_darwin_386.go
index 9f47b87..6103f21 100644
--- a/vendor/golang.org/x/sys/unix/ztypes_darwin_386.go
+++ b/vendor/golang.org/x/sys/unix/ztypes_darwin_386.go
@@ -145,6 +145,10 @@
 	_       [3]byte
 }
 
+const (
+	PathMax = 0x400
+)
+
 type RawSockaddrInet4 struct {
 	Len    uint8
 	Family uint8