mailmanctl doesn't setgroups when run as root

[Ppsys]

When mailmanctl is executed as root the checkprivs
function performs setgid and setuid to reduce the
process privileges.

But mailmanctl fails to set the supplemental groups of
the process to those of the setuid'ed user, effectively
leaving the
processes with the same group privileges as root and,
potentially, without the group privileges of the
setuid'ed user.

This patch uses os.setgroups() to fix that.

Problem definition and solution by Jonas Meurer.

I'm just filing the bug fix for him.

Apply the patch from within the Mailman build directory
with:

patch -p1 < path-to-patch-file

[http://sourceforge.net/tracker/index.php?func=detail&aid=777444&group_id=103&atid=100103]

[Ppsys (ppsys)]

grpsec-2.1.3-0.1.patch is a MM 2.1.3 compatible version of the
patch

[Barry Warsaw (barry)]

Accepted for Mailman 2.1.4, with a slight recoding; note
that os.setgroups() isn't available in Python 2.1, which we
still support.