solr SearchHandler扩展，解决httpclient连接问题以及对连接异常的容错处理

<requestHandler name="standard2" class="solr.SearchHandlerExt" > <lst name="defaults"> <str name="echoParams">explicit</str><str name="timeAllowed">2000</str><str name="defType">dismax</str><str name="qf">title^2 tag^1</str><str name="q.op">AND</str><str name="bf">10</str><str name="start">0</str><str name="rows">10</str><str name="debugQuery">on</str><str name="q">*:*</str> <str name="shards">localhost:3456/solr,localhost:8080/solr</str><str name="shards.qt">single</str> <str name="shards.tolerant">true</str> </lst> </requestHandler>