MAPREDUCE-5414. TestTaskAttempt fails in JDK7 with NPE. Contributed by Nemon Lou.



git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1520964 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-HDFS-4310-trunk-gd