[SPARK-22173][WEB-UI] Table CSS style needs to be adjusted in History Page and in Executors Page.

## What changes were proposed in this pull request?

There is a problem with table CSS style.

1. At present, table CSS style is too crowded, and the table width cannot adapt itself.

2. Table CSS style is different from job page, stage page, task page, master page, worker page, etc. The Spark web UI needs to be consistent.

fix before:
![01](https://user-images.githubusercontent.com/26266482/31041261-c6766c3a-a5c4-11e7-97a7-96bd51ef12bd.png)

![02](https://user-images.githubusercontent.com/26266482/31041266-d75b6a32-a5c4-11e7-8071-e3bbbba39b80.png)

----------------------------------------------------------------------------------------------------------

fix after:
![1](https://user-images.githubusercontent.com/26266482/31041162-808a5a3e-a5c3-11e7-8d92-d763b500ce53.png)

![2](https://user-images.githubusercontent.com/26266482/31041166-86e583e0-a5c3-11e7-949c-11c370db9e27.png)

## How was this patch tested?

manual tests

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: guoxiaolong <guo.xiaolong1@zte.com.cn>

Closes #19397 from guoxiaolongzte/SPARK-22173.

core/src/main/scala/org/apache/spark/deploy/history/HistoryPage.scala

@@ -37,7 +37,7 @@ private[history] class HistoryPage(parent: HistoryServer) extends WebUIPage("")
     val content =
       <script src={UIUtils.prependBaseUri("/static/historypage-common.js")}></script>
       <div>
-          <div class="span12">
+          <div class="container-fluid">
             <ul class="unstyled">
               {providerConfig.map { case (k, v) => <li><strong>{k}:</strong> {v}</li> }}
             </ul>
@@ -58,7 +58,7 @@ private[history] class HistoryPage(parent: HistoryServer) extends WebUIPage("")
             {
             if (allAppsSize > 0) {
               <script src={UIUtils.prependBaseUri("/static/dataTables.rowsGroup.js")}></script> ++
-                <div id="history-summary" class="span12 pagination"></div> ++
+                <div id="history-summary" class="row-fluid"></div> ++
                 <script src={UIUtils.prependBaseUri("/static/utils.js")}></script> ++
                 <script src={UIUtils.prependBaseUri("/static/historypage.js")}></script> ++
                 <script>setAppLimit({parent.maxApplications})</script>

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" class="span12 pagination"></div> ++
+          <div id="active-executors" class="row-fluid"></div> ++
           <script src={UIUtils.prependBaseUri("/static/utils.js")}></script> ++
           <script src={UIUtils.prependBaseUri("/static/executorspage.js")}></script> ++
           <script>setThreadDumpEnabled({threadDumpEnabled})</script>