HDFS-4302. Fix fatal exception when starting NameNode with DEBUG logs. Contributed by Eugene Koontz.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1428591 13f79535-47bb-0310-9956-ffa450edef68
Merge branch 'branch-2' of github.com:griddynamics/yhadoop-common into branch-2-gd
Merge branch 'branch-2-gd' of github.com:griddynamics/yhadoop-common into fb-xxx-java7-library-path-branch-2-gd