[OE-core] user and group default policies

[Mark Hatle]

With shadow-utils enabled, a default user and group add policy is installed in
/etc/default/adduser.  This policy specifies that group "1000" is used when
adding new users, unless you specify a group.

Well, we don't have a user 1000 by default, which results in the warning:

useradd: group '1000' does not exist
useradd: the GROUP= configuration in /etc/default/useradd will be ignored

So my question is -- how should we resolve this.  What I see are a couple of
possibilities:

1) We create a default user "group"..  We then adjust the /etc/default/useradd
to use that number... (if we don't user 1000 we'd have to change it.)

2) Remove that setting..  I believe this means that useradd will always add a
group for each user added.

3) -- we do something else..

Any comments?  I'd like to fix this -- but I'm not sure historically if OE has
had a policy on this, or if we need to create one.. If we create one, it needs
to be reasonable for the majority of the oe-core uses.

--Mark