Cherry pick from master branch

    * Remove error code during creation existing directory

      Closes-bug: #1269319

    * Fix issues in admin guide

      * comments mentioned in https://review.openstack.org/#/c/65926/
      * document style (XML style, formatting issues)

      Closes-Bug: 1268537

Change-Id: I726d8b8849b2ccd44fdbf9d7b4ce65f3a62cf4aa