@Override
  public void addCacheListener(SystemMemberCacheListener listener) {
    synchronized (cacheListLock) {
      // never modify cacheListeners in place.
      // this allows iteration without concurrent mod worries
      List oldListeners = cacheListeners;
      if (!oldListeners.contains(listener)) {
        List newListeners = new ArrayList(oldListeners);
        newListeners.add(listener);
        cacheListeners = newListeners;
      }
    }
  }
returns instance of AdminDistributedSystem that is current connected. See
<code>thisAdminDS</code>. (for feature requests #32887)
<p>
TODO: remove this static method during reimplementation of
{@link SystemMemberCacheEventProcessor}
geode-core/src/main/java/org/apache/geode/admin/internal/AdminDistributedSystemImpl.java