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

This reverts commit 5845a62.

This was reverted because it broke compilation for branch-1.2.  The problem is
that the `requestedIncomplete` variable is not defined in this branch.

Author: JoshRosen

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

@@ -57,8 +57,6 @@ private[spark] 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?