display-access-file: maintain FamilyLocal entry for backward compatibility

commit 0fccf4e0 swapped out the
FamilyLocal auth cookie for a FamilyWild auth cookie, because the
latter is more resilient to hostname changes.  Unfortunately,
not all of the tooling accepts FamilyWild cookies (in particular the
xauth command), so things like su broke.

This commit changes the code to have a FamilyWild and FamilyLocal
cookie.

https://bugzilla.gnome.org/show_bug.cgi?id=690562