fix to make mkdirs(..) tolerant of existing directories during a distrib...

The mkdirs(..) operation across the distributed file system may race other nodes during full path creation.  mkdirs(..) should not cause errors if directories or partial directory exists but instead continue the creation flow until the full path is created. 

This notion is documented in Cs RawLocalFileSystem source code as: "Creates the specified directory hierarchy. Does not treat existence as an error."  which is visible here:

http://grepcode.com/file/repository.cloudera.com/content/repositories/releases/com.cloudera.hadoop/hadoop-core/0.20.2-320/org/apache/hadoop/fs/RawLocalFileSystem.java#RawLocalFileSystem.mkdirs%28org.apache.hadoop.fs.Path%29


The mkdirs(..) patch logic is lifted from the same source.