suse-add_ip.sh: do not set default route on venet0 when no IPs

suse-add_ip.sh always set default route on venet0 even if no IP address
specified. This commit fixes it.

Unfortunately, it does not take $IPV6 into account but still improves
current behavior.

[kir@openvz.org: use 'elif' and '[ ]' to be in-line with script style]
1 file changed