LU-2302 scripts: make lfs_migrate compatible with 1.8

LU-2302 scripts: make lfs_migrate compatible with 1.8

Earlier versions of lfs setstripe/getstripe use option -s instead
of -S. Make sure lfs_migrate can be used with any version.

Signed-off-by: Daniel Kobras <d.kobras@science-computing.de>
Signed-off-by: Keith Mannthey <keith.mannthey@intel.com>
Change-Id: Ic3caaeaf3d6c764afbd75cd7a8a7279462d21d47
Reviewed-on: http://review.whamcloud.com/4702
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>