[HDFS-460] Add kerberos docs for HDFS (#1952)
[HDFS-460] Add kerberos docs for HDFS (#1952)

* Add kerberos docs for HDFS

* Add data nodes note

* Fix spelling

vishnu2kmohan/dcos-commons,mesosphere/dcos-commons,vishnu2kmohan/dcos-commons,vishnu2kmohan/dcos-commons,mesosphere/dcos-commons,mesosphere/dcos-commons,vishnu2kmohan/dcos-commons,mesosphere/dcos-commons,mesosphere/dcos-commons,vishnu2kmohan/dcos-commons