LU-6974 util: set max_sectors_kb properly

LU-6974 util: set max_sectors_kb properly

Reduce max_sectors_kb to avoid crash on some special block devices.

Test-Parameters: alwaysuploadlogs envdefinitions=SLOW=yes,ENABLE_QUOTA=yes 	mdtfilesystemtype=ldiskfs mdsfilesystemtype=ldiskfs 	ostfilesystemtype=ldiskfs clientdistro=el7 ossdistro=el7 	mdsdistro=el7 mdtcount=1 testlist=runtests
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: Ifc7efd169f0db0b54c3f727fc65716c203930e29
Reviewed-on: http://review.whamcloud.com/16116
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>