LU-8006 ptlrpc: specify ordering of TBF policy rules

LU-8006 ptlrpc: specify ordering of TBF policy rules

With this patch, when inserting a new rule, the rank of the rule
can be given by "start" command. Also, the rank of the rule can be
changed by command of "change".

lctl set_param ost.OSS.ost_io.nrs_tbf_rule=
	"start $NAME jobid={$ID} rate=$RATE rank=$NEXT"
lctl set_param ost.OSS.ost_io.nrs_tbf_rule=
	"change $NAME rate=$RATE rank=$NEXT"

$NAME is the target rule name. $NEXT is the rule name that the target
rule will be moved before.

Signed-off-by: Li Xi <lixi@ddn.com>
Change-Id: I6b465342365d6c09710616cd3c9e068b66a8fc89
Reviewed-on: http://review.whamcloud.com/19476
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Gu Zheng <gzheng@ddn.com>
Reviewed-by: Emoly Liu <emoly.liu@intel.com>
Reviewed-by: Wang Shilong <wshilong@ddn.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>