HADOOP-9524. Fix ShellCommandFencer to work on Windows. Contributed by Arpit Agarwal.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1476856 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4734. HDFS Tests that use ShellCommandFencer are broken on Windows. Contributed by Arpit Agarwal.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1476877 13f79535-47bb-0310-9956-ffa450edef68