Fix bug where mkdir_on_hdfs not work correctly on Hadoop 2.2 / 0.23.

For 2.x & 0.23, mkdir need -p for creating parent directories:

http://hadoop.apache.org/docs/r2.2.0/hadoop-project-dist/hadoop-common/FileSystemShell.html#mkdir
http://hadoop.apache.org/docs/r0.23.10/hadoop-project-dist/hadoop-common/FileSystemShell.html#mkdir


For 1.x & 0.1x & 0.20, mkdir doesn't need any additional parameters:
http://hadoop.apache.org/docs/r1.2.1/file_system_shell.html#mkdir