discovery: make GlobalDiscovery public

Change-Id: I7076d235a7c2291cb3cc9546e7486d9103cde2eb
diff --git a/lib/src/main/java/io/v/impl/google/lib/discovery/GlobalDiscovery.java b/lib/src/main/java/io/v/impl/google/lib/discovery/GlobalDiscovery.java
index 04b0ce6..9031baa 100644
--- a/lib/src/main/java/io/v/impl/google/lib/discovery/GlobalDiscovery.java
+++ b/lib/src/main/java/io/v/impl/google/lib/discovery/GlobalDiscovery.java
@@ -16,7 +16,7 @@
  * TODO(jhahn): This is an experimental work to see its feasibility and set
  * the long-term goal, and can be changed without notice.
  */
-class GlobalDiscovery {
+public class GlobalDiscovery {
     private static native Discovery nativeNewDiscovery(
             VContext ctx, String path, Duration mountTtl, Duration scanInterval) throws VException;