init.d/vz-gentoo: fix a typo

As reported in

http://forum.openvz.org/index.php?t=msg&th=12775&S=cec69936a4b7d441bf7f44478dbb6c3c#msg_51690

there's a missing bracket.

This is a fix to commit 8e7fdb5.

Reported-by: Sergey Ya Korshunoff
Signed-off-by: Kir Kolyshkin <kir@openvz.org>