Fix for HADOOP-82. Completes count should never be less than zero. Contributed by Michael Stack.

git-svn-id: https://svn.apache.org/repos/asf/lucene/hadoop/trunk@386226 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/hadoop/mapred/TaskInProgress.java

@@ -268,7 +268,9 @@ class TaskInProgress {
             status.setRunState(TaskStatus.FAILED);
         }
         this.recentTasks.remove(taskid);
-        this.completes--;
+        if (this.completes > 0) {
+            this.completes--;
+        }
 
         numTaskFailures++;
         if (numTaskFailures >= MAX_TASK_FAILURES) {