LU-5814 lov: remove LSM from struct lustre_md

In struct lustre_md replace the stuct lov_stripe_md *lsm member with
an opaque struct lu_buf layout which holds the layout metadata
returned by the server. Refactor the LOV object initialization and
layout change code to accommodate this. Simplify lov_unpackmd() and
supporting functions according to the reduced number of use cases.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: Iac44ba479556693932bae0b9878565155b609e07
Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-on: http://review.whamcloud.com/13722
Tested-by: Jenkins
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>