MapRed History server start does not create directories in HDFS when WEBHDFS is disabled.

MapRed HistoryServer start logic (implemented in yarn.py) creates various dirs in HDFS. The dir creation only runs thru when WEBHDFS is enabled. When WEBHDFS is disabled, HdfsResource calls bailed with NPE as the following one.

Creating: Resource [source=null, target=/app-logs, type=directory, action=create, owner=yarn, group=hadoop, mode=777, recursiveChown=false, recursiveChmod=true, changePermissionforParents=false, manageIfExists=false]
Exception occurred, Reason: null
java.lang.NullPointerException
at org.apache.hadoop.fs.FileSystem.fixRelativePart(FileSystem.java:2211)
at org.apache.hadoop.hdfs.DistributedFileSystem.getFileStatus(DistributedFileSystem.java:1300)
at org.apache.hadoop.fs.FileSystem.exists(FileSystem.java:1426)
at org.apache.ambari.fast_hdfs_resource.Runner.main(Runner.java:80)