When updating iproute2 to the current stable this moves /sbin/ip to /bin/ip. An existing util-vserver package (no update available) then references the wrong path /usr/lib64/util-vserver/util-vserver-vars:131:_IP="/sbin/ip" which breaks the network start of any vserver at the next reboot.
For the record ~util-vserver-0.30.216_pre3038 fixes that issue.