LU-15141 quota: optimize capability check for root squash

LU-15141 quota: optimize capability check for root squash

On client side, checking for owner/group quota can be directly
bypassed if this is for root and there is no root squash.

Lustre-change: https://review.whamcloud.com/45322
Lustre-commit: TBD (15aa2e9264f0604b185ce280df4b34ea5a280b3f)

Change-Id: If29eca428d8748df412a717615e4d0a4886ddd04
Fixes: 0b057b7179 ("LU-14739 quota: nodemap squashed root cannot bypass quota")
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-on: https://review.whamcloud.com/45321
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>