vz.conf: fix a typo

s/с/c/

This is funny, but somehow a cyrillic 'c' appeared in vz.conf.

https://bugzilla.openvz.org/3023

Reported-by: Evgenii Terechkov <evg@altlinux.org>
Signed-off-by: Kir Kolyshkin <kir@openvz.org>