LU-4738 lmv: access lum_stripe_offset as little endian

LU-4738 lmv: access lum_stripe_offset as little endian

By the time that a struct lmv_user_md reaches lmv_placement_policy()
it has already been converted to little endian. Therefore use the
appropriate macros around accesses to this this field. This issue was
found by rewriting the definition of struct lmv_user_md to use the
__leXX typedefs and running sparse.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: If641375eabd22cc3e935a2e8f1327c48081c6ed1
Reviewed-on: http://review.whamcloud.com/9671
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Swapnil Pimpale <spimpale@ddn.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>