OpenCensusUtils does need to be public (#569)

Author: chingor13

google-http-client/src/main/java/com/google/api/client/http/OpenCensusUtils.java

@@ -40,7 +40,7 @@
  * @author Hailong Wen
  * @since 1.28
  */
-class OpenCensusUtils {
+public class OpenCensusUtils {
 
   private static final Logger logger = Logger.getLogger(OpenCensusUtils.class.getName());