Update OWNERS.

Change-Id: Ib069b181fd48d73e5320f44c435b8814f269d291
diff --git a/fs_mgr/libsnapshot/OWNERS b/fs_mgr/libsnapshot/OWNERS
index 9d2b877..1ee4175 100644
--- a/fs_mgr/libsnapshot/OWNERS
+++ b/fs_mgr/libsnapshot/OWNERS
@@ -3,3 +3,4 @@
 dvander@google.com
 elsk@google.com
 akailash@google.com
+zhangkelvin@google.com