LUDOC-328 tbf: add HTC strategy to NRS-TBF section

LUDOC-328 tbf: add HTC strategy to NRS-TBF section

Update NRS-TBF policy section to reflect Hard Token Compensation
(HTC) strategy:
- meet realtime requirement with a new rule option "realtime=1"
- Lustre-commit: d11fa2c279593634cf6c4196b413a6d285b24e10
- Lustre-change: http://review.whamcloud.com/26087

Change-Id: I07ece7bd3022351a7f71d1ba9cfd2193d8261ccd
Signed-off-by: Emoly Liu <emoly.liu@intel.com>
Reviewed-on: https://review.whamcloud.com/31628
Tested-by: Jenkins
Reviewed-by: Joseph Gmitter <joseph.gmitter@intel.com>