LU-15393 lod: skip qos for qos_threshold_rr=100

LU-15393 lod: skip qos for qos_threshold_rr=100

Current implementation of qos allocation is called for
every statfs update. It takes lq_rw_sem for write and
recalculate penalties, even whith setting qos_threshold_rr=100.
Which means always use rr allocation. Let's skip unnecessary
locking and calculation for 100% round robin allocation.

Lustre-change: https://review.whamcloud.com/46388
Lustre-commit: 2f23140d5c1396fd0b247bd7f9c249f6e24096b7

HPE-bug-id: LUS-10388
Signed-off-by: Alexander Boyko <alexander.boyko@hpe.com>
Change-Id: I2fcc272d00a988ca4ba0f745b1d5809d65b28654
Reviewed-on: https://review.whamcloud.com/48206
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>