[SPARK-21060][WEB-UI]Css style about paging function is error in the executor page. Css style about paging function is error in the executor page. It is different of history server ui paging function css style.

core/src/main/scala/org/apache/spark/ui/exec/ExecutorsPage.scala

@@ -82,7 +82,7 @@ private[ui] class ExecutorsPage(
               </ul>
             </div>
           </div> ++
-          <div id="active-executors"></div> ++
+          <div id="active-executors" class="span12 pagination"></div> ++
           <script src={UIUtils.prependBaseUri("/static/utils.js")}></script> ++
           <script src={UIUtils.prependBaseUri("/static/executorspage.js")}></script> ++
           <script>setThreadDumpEnabled({threadDumpEnabled})</script>