truss /usr/bin/su
login (or not if root)
then exit the shell

truss will get stuct in tsleep

I dont know if this is correct, but it fixes the problem and
according to the commends in pioctl.h, PF_ISUGID is set when we
want to ignore UID changes.

The code is checking for when PF_ISUGID is not set and since it
never is set, we always ignore UID changes.

Submitted by: Paul Saab <ps@yahoo-inc.com>