LU-941 hsm: Manage dirty flag for hsm-archived files

LU-941 hsm: Manage dirty flag for hsm-archived files

clio manages a LLIF_DATA_MODIFIED flag when file data are modified
which is sent to MDT. It now has a way to know file data was modified
and can update HS_DIRTY flag in LMA which is mandatory for Lustre/HSM
binding.
When HS_DIRTY is set, a changelog event is raised.

Signed-off-by: Aurelien Degremont <aurelien.degremont@cea.fr>
Change-Id: I074c8db0d6c10341aaabc55441fe746497259e84
Reviewed-on: http://review.whamcloud.com/1891
Tested-by: Hudson
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>