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.

Change-Id: If29eca428d8748df412a717615e4d0a4886ddd04
Fixes: a4fbe7341b ("LU-14739 quota: nodemap squashed root cannot bypass quota")
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-on: https://review.whamcloud.com/45322
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>