LU-19058 llite: ll_statfs_project for projid 0

LU-19058 llite: ll_statfs_project for projid 0

df should take into account project quota limits for
squashed project id. Otherwhise it shows system wide
size.

Signed-off-by: Sergey Cheremencev <scherementsev@ddn.com>
Change-Id: Ieae5d8503829e2de859b60ed259bc0ee4d1274ca
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/59435
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>