title: CloseableHttpClient connection pool shut down
body: <p>when I use CloseableHttpClient and do excute method , it works normally at the first time but never successed after . 
  it will throw exception which said "Connection pool shut down"</p>
  
  <p>someone said it because I haven't close the client 
  someone said is a bug in httpclient 4.3</p>
  
  <p>my project doesn't exist the issue above ,but it still doesn't work will</p>
  
  <pre><code>CloseableHttpClient httpClient = HttpClientManagerUtils.getHttpClient();
  
      try {
          HttpResponse response = httpClient.execute(httpPost);
          if (response.getStatusLine().getStatusCode() == 200) {
              log.info("调用网易接口成功,url:{},param:{}", url, JSONObject.toJSON(param));
              HttpEntity entity = response.getEntity();
              if (entity.getContentType().toString().contains("application/json")) {
                  String responseString = EntityUtils.toString(entity, "utf-8");
                  return JSON.toJavaObject(JSON.parseObject(responseString), NimResult.class);
              }
          } else {
              throw new RuntimeException("http code : " + response.getStatusLine().getStatusCode() + ", exception:" +
                      EntityUtils.toString(response.getEntity()));
          }
      } catch (Exception e) {
          log.error("调用网易接口异常,url:{},param:{}", url, JSONObject.toJSON(param), e);
      } finally {
          httpClient.close();
      }
  </code></pre>