xfs_quota: fall back silently if XFS_GETNEXTQUOTA fails

xfs_quota: fall back silently if XFS_GETNEXTQUOTA fails

After XFS_GETNEXTQUOTA feature has been merged into linux kernel and
xfsprogs, xfs_quota use Q_XGETNEXTQUOTA for report and dump, and
fall back to old XFS_GETQUOTA ioctl if XFS_GETNEXTQUOTA fails.

But when XFS_GETNEXTQUOTA fails, xfs_quota print a warning as
"XFS_GETQUOTA: Invalid argument". That's due to kernel can't
recognize XFS_GETNEXTQUOTA ioctl and return EINVAL. At this time,
the warning is helpless, xfs_quota just need to fall back.

Signed-off-by: Zorro Lang <zlang@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>