Fix to Stage UI to display numbers on progress bar

Fixes an issue on Stage UI to display numbers on progress bar which are today hidden behind the progress bar div.

Author: emtiazahmed

core/src/main/scala/org/apache/spark/ui/jobs/StageTable.scala

@@ -63,7 +63,7 @@ private[ui] class StageTable(stages: Seq[StageInfo], parent: JobProgressUI) {
     val startWidth = "width: %s%%".format((started.toDouble/total)*100)
 
     <div class="progress">
-      <span style="text-align:center; position:absolute; width:100%;">
+      <span style="text-align:center; position:absolute; width:100%; left:0;">
         {completed}/{total} {failed}
       </span>
       <div class="bar bar-completed" style={completeWidth}></div>