Description of problem:
It looks for me like there is no way to specify ethernet device name to be created inside the openvz container. At least I couldn't find such info at http://libvirt.org/formatdomain.html#elementsNICS.
If I do as below I get br0 as ethernet device inside VM whereas I'd like it to be eth0.

Version-Release number of selected component (if applicable):
ovzkernel release is 2.6.18-194.26.1.el5.028stab081.1, vzctl-3.0.26-1, OS is CentOS 5.5, libvirt/virsh version is 0.8.8, 

How reproducible:
$ cat ovz.xml
<domain type='openvz' id='144'>
  <name>144</name>
  <uuid>0071c128-58b4-4688-be17-1e062a22b36c</uuid>
  <vcpu>1</vcpu>
  <memory>524288</memory>
  <os>
    <type>exe</type>
    <init>/sbin/init</init>
  </os>
  <devices>
    <filesystem type='template'>
      <source name='centos-5-x86'/>
      <target dir='/'/>
    </filesystem>
    <interface type='bridge'>
      <source bridge='br0'/>
    </interface>
  </devices>
</domain>

$ virsh create ovz.xml
Domain 144 created from ovz.xml


Actual results:
$ grep -i netif /etc/vz/conf/144.conf
NETIF="ifname=br0,bridge=br0,mac=52:54:00:74:DD:F3,host_ifname=veth144.0,host_mac=52:54:00:06:78:76"


Expected results:
$ grep -i netif /etc/vz/conf/144.conf
NETIF="ifname=eth0,bridge=br0,mac=52:54:00:74:DD:F3,host_ifname=veth144.0,host_mac=52:54:00:06:78:76"


Additional info:
One of the possible reason of observing behaviour is the syntax of vzctl commands had been changed since 3.0.22 version as it's written at http://wiki.openvz.org/Veth#syntax_vzctl_version_.3E_3.0.22.