base-files: default_postinst() fix variable colision

The name variable contains at first the package name,
and after the last group name.
This patch fixes /etc/rc.d symlink creation (at least).

Change name in pkgname, change the other name in ugname
(user group name), and id in ugid (user group id)

Signed-off-by: Etienne CHAMPETIER <champetier.etienne@gmail.com>

SVN-Revision: 44253