zdtm.py: exclude a vsyscall vma for x32 tests

We alwasy exclude vsyscall vma-s for x32 tests, but
this part was broken by python3 patches.

1: Old maps lost: set([])
1: New maps appeared: set([u"ffffffffff600000-ffffffffff601000 [u'r-xp']"])

Reported-by: Mr Jenkins
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>