@Override
          public void complete() {
            latch.countDown();
          }
Get a set of stats from all connections.

@param arg which stats to get
@return a Map of the server SocketAddress to a map of String stat keys to
        String stat values.
@throws IllegalStateException in the rare circumstance where queue is too
          full to accept any more requests
src/main/java/net/spy/memcached/MemcachedClient.java