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>
LU-2444 build: fix 'error handling' issues

Fix 'error handling issues' defects found by Coverity version
6.0.3:
Unchecked return value (CHECKED_RETURN)
Value returned from a function is not checked for errors before
being used.
Argument cannot be negative (NEGATIVE_RETURNS)
Negative value used as argument to a function expecting a
positive value.

Signed-off-by: Sebastien Buisson <sebastien.buisson@bull.net>
Change-Id: I44022a7d7227ee46345b77701b4c5199a74c386d
Reviewed-on: http://review.whamcloud.com/4772
Tested-by: Hudson
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Keith Mannthey <keith.mannthey@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>