[SPARK-21250][WEB-UI] Add a url in the table of 'Running Executors' in worker...

[SPARK-21250][WEB-UI] Add a url in the table of 'Running Executors' in worker page to visit job page.

## What changes were proposed in this pull request?

Add a url in the table of 'Running Executors' in worker page to visit job page.

When I click URL of 'Name', the current page jumps to the job page. Of course this is only in the table of 'Running Executors'.

This URL of 'Name' is in the table of 'Finished Executors' does not exist, the click will not jump to any page.

fix before:
![1](https://user-images.githubusercontent.com/26266482/27679397-30ddc262-5ceb-11e7-839b-0889d1f42480.png)

fix after:
![2](https://user-images.githubusercontent.com/26266482/27679405-3588ef12-5ceb-11e7-9756-0a93815cd698.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 #18464 from guoxiaolongzte/SPARK-21250.

core/src/main/scala/org/apache/spark/deploy/worker/ui/WorkerPage.scala

@@ -23,8 +23,8 @@ import scala.xml.Node
 
 import org.json4s.JValue
 
+import org.apache.spark.deploy.{ExecutorState, JsonProtocol}
 import org.apache.spark.deploy.DeployMessages.{RequestWorkerState, WorkerStateResponse}
-import org.apache.spark.deploy.JsonProtocol
 import org.apache.spark.deploy.master.DriverState
 import org.apache.spark.deploy.worker.{DriverRunner, ExecutorRunner}
 import org.apache.spark.ui.{UIUtils, WebUIPage}
@@ -112,7 +112,15 @@ private[ui] class WorkerPage(parent: WorkerWebUI) extends WebUIPage("") {
       <td>
         <ul class="unstyled">
           <li><strong>ID:</strong> {executor.appId}</li>
-          <li><strong>Name:</strong> {executor.appDesc.name}</li>
+          <li><strong>Name:</strong>
+          {
+            if ({executor.state == ExecutorState.RUNNING} && executor.appDesc.appUiUrl.nonEmpty) {
+              <a href={executor.appDesc.appUiUrl}> {executor.appDesc.name}</a>
+            } else {
+              {executor.appDesc.name}
+            }
+          }
+          </li>
           <li><strong>User:</strong> {executor.appDesc.user}</li>
         </ul>
       </td>