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/drm/drmserver/DrmManager.cpp b/drm/drmserver/DrmManager.cpp
index 537791c..49df1c8 100644
--- a/drm/drmserver/DrmManager.cpp
+++ b/drm/drmserver/DrmManager.cpp
@@ -117,7 +117,11 @@
 status_t DrmManager::setDrmServiceListener(
             int uniqueId, const sp<IDrmServiceListener>& drmServiceListener) {
     Mutex::Autolock _l(mLock);
-    mServiceListeners.add(uniqueId, drmServiceListener);
+    if (NULL != drmServiceListener.get()) {
+        mServiceListeners.add(uniqueId, drmServiceListener);
+    } else {
+        mServiceListeners.removeItem(uniqueId);
+    }
     return DRM_NO_ERROR;
 }