LUDOC-34 remove modules with 'lustre_rmmod'

LUDOC-34 remove modules with 'lustre_rmmod'

Use "lustre_rmmod" instead of
"lctl modules | awk '{print $2}' | xargs rmmod" to remove modules.
(Corrected tip in section 15.2.2)

Change-Id: I833f83a85e87d00427ed41180e0db6fa51074d2d
Signed-off-by: Przemyslaw Dubaniewicz <przemyslaw@dubaniewicz.com>
Reviewed-on: http://review.whamcloud.com/5668
Tested-by: Hudson
Reviewed-by: Cliff White <cliff.white@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>