Stop pkgsrc users from appearing in the OSX login window

[Jonathan Perkin <jperkin%joyent.com@localhost>]

For a while $SUBJECT has bothered me, so recently I fixed it for our
2015Q3 packages using this diff (nabbed from a StackOverflow post):

  --- a/sysutils/user_darwin/files/useradd.sh
  +++ b/sysutils/user_darwin/files/useradd.sh
  @@ -99,2 +99,3 @@ else
       dscl . -create /users/$user Password '*'
  +    dscl . -delete /users/$user AuthenticationAuthority
   fi

Anyone have a reason I shouldn't commit this?

Thanks,

-- 
Jonathan Perkin  -  Joyent, Inc.  -  www.joyent.com