Fix permissions of tempfile

Signed-off-by: Sevag Hanssian <sevag.hanssian@gmail.com>

prometheus/registry.go

@@ -562,6 +562,10 @@ func WriteToTextfile(filename string, g Gatherer) error {
 	if err := tmp.Close(); err != nil {
 		return err
 	}
+
+	if err := os.Chmod(tmp.Name(), 0644); err != nil {
+		return err
+	}
 	return os.Rename(tmp.Name(), filename)
 }