Turn on rgrplvb by default for sb_fs_format > 1801.

Mount options still have to override this so a new args field to
differentiate between 'off' and 'not specified' is added, and the new
default is applied only when it's not specified.
Signed-off-by: NAndrew Price <anprice@redhat.com>
Signed-off-by: NAndreas Gruenbacher <agruenba@redhat.com>