xfs_quota: Don't ignore every error when asking for quota

xfs_quota: Don't ignore every error when asking for quota

Errors from quotactl() were silently ignored like:

$ xfs_quota -x -c "report -u -L 12000 -U 12001"
$

Print error messages for conditions other than ENOENT and ENOSYS
(these two aren't actually errors for the way quotactl is used).

We now get:

$ ./xfs_quota -x -c "report -u -L 12000 -U 12001"  /home
XFS_GETQUOTA: Operation not permitted
XFS_GETQUOTA: Operation not permitted
$

which is consistent with error reporting in rest of quotactl using code.

Reviewed-by: Christoph Hellwig <hch@lst.de>