LU-2482 layout: introduce new layout for released files

LU-2482 layout: introduce new layout for released files

Released files now have a standard layout (with generation, pool, ...)
and a stripe count 0 and lmm_pattern flag LOV_PATTERN_F_RELEASED.

Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Signed-off-by: Johann Lombardi <johann.lombardi@intel.com>
Change-Id: Id2c3b95fdd304f803d391281a86927f5c93cb3b4
Reviewed-on: http://review.whamcloud.com/4816
Reviewed-by: Keith Mannthey <keith.mannthey@intel.com>
Tested-by: Hudson
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>