OpenDelta: Do not leak service connection

We bind using the old API so we should also unbind.
bind onCreate so symmetricly unbind onDestroy

src/eu/chainfire/opendelta/MainActivity.java

@@ -751,6 +751,12 @@ public class MainActivity extends Activity {
         }
     }
 
+    @Override
+    public void onDestroy() {
+        unbindService(mConnection);
+        super.onDestroy();
+    }
+
     private boolean isExternalStorageDocument(Uri uri) {
         return "com.android.externalstorage.documents".equals(uri.getAuthority());
     }