DRM Framework bug fixes.

- Make sure to clean-up obsolete listeners.
- Close cursor after using it.
- Add virtual destructor to the base class of OnInfoListener.

Changes are made by SEMC and Sony.

Change-Id: Ibb6dd625ef48e3597188f0d7c90f9d4c780b6139
diff --git a/include/drm/DrmManagerClient.h b/include/drm/DrmManagerClient.h
index 3dbfbe2..004556f 100644
--- a/include/drm/DrmManagerClient.h
+++ b/include/drm/DrmManagerClient.h
@@ -49,6 +49,9 @@
     class OnInfoListener: virtual public RefBase {
 
     public:
+        virtual ~OnInfoListener() {}
+
+    public:
         virtual void onInfo(const DrmInfoEvent& event) = 0;
     };