vzctl set --ipadd/ipdel: support for Fedora 18 CT

First, in F18 ifconfig is not included by default, so we (finally) use
ip instead.

Second, it doesn't like having 127.0.0.1 on venet0, the simplest way to
make it like it is to have ARPCHECK="no" in ifcfg-venet0 file.

Slightly tested here and there, looks like it works.

Heavily based on patch by Konstantin Volkov <wolf@parallels.com>,
with all the bugs added by me.

Signed-off-by: Kir Kolyshkin <kir@openvz.org>
3 files changed