[SPARK-5634] [core] Show correct message in HS when no incomplete apps f...

...ound.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #5515 from vanzin/SPARK-5634 and squashes the following commits:

f74ecf1 [Marcelo Vanzin] [SPARK-5634] [core] Show correct message in HS when no incomplete apps found.

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

@@ -90,6 +90,8 @@ private[history] class HistoryPage(parent: HistoryServer) extends WebUIPage("")
                 </span>
               </h4> ++
               appTable
+            } else if (requestedIncomplete) {
+              <h4>No incomplete applications found!</h4>
             } else {
               <h4>No completed applications found!</h4> ++
               <p>Did you specify the correct logging directory?