LU-5814 lov: add cl_object_layout_get()

LU-5814 lov: add cl_object_layout_get()

Add cl_object_layout_get() to return the layout and generation of an
object. Replace some direct accesses to object LSM with calls to this
function.

In ll_getxattr() factor out the LOV xattr specific handling into a new
function ll_getxattr_lov() which calls cl_object_layout_get(). In
ll_listxattr() call ll_getxattr_lov() to determine if a lustre.lov
xattr should be emitted.  Add lov_lsm_pack() to generate LOV xattrs
from a LSM.

Remove the unused functions ccc_inode_lsm_{get,put}() and
lov_lsm_get().

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Change-Id: If0d7696473848c8eace3c5b03c016514bc28509f
Reviewed-on: http://review.whamcloud.com/13680
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>