staging/lustre: Fix unsafe userspace access in many proc files

Apparently we are pretty bad about verifying our buffers passed
from userspace.

Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Reviewed-on: http://review.whamcloud.com/9059
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4563
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>