LU-4810 utils: print messages when set tunables

When set scheduler and max_sectors_kb on mount, error messages should
be printed to notify user that these tunables are changed by lustre.

Signed-off-by: Niu Yawei <yawei.niu@intel.com>
Change-Id: I6a3618b7e5eb0127e9aea18631397cd4dcbde546
Reviewed-on: http://review.whamcloud.com/9865
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Blake Caldwell <blakec@ornl.gov>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>